Remove long double conversion work-arounds (HDFGroup#3097)

Several options and public symbols that were provided to paper
      over non-standard long double conversions between signed/unsigned
      long and long long values were removed from the Autotools and
      CMake. These were added twenty years ago, when C99 and 64-bit
      platforms were less common and are no longer needed.

      Autotools:
        --enable-dconv-accuracy

      CMake:
        HDF5_WANT_DATA_ACCURACY

      H5pubconf.h symbols:
        H5_WANT_DATA_ACCURACY
        H5_LDOUBLE_TO_LONG_SPECIAL
        H5_LONG_TO_LDOUBLE_SPECIAL
        H5_LDOUBLE_TO_LLONG_ACCURATE
        H5_LLONG_TO_LDOUBLE_CORRECT
        H5_DISABLE_SOME_LDOUBLE_CONV

config/cmake/ConfigureChecks.cmake

@@ -570,19 +570,6 @@ if (HDF5_STRICT_FORMAT_CHECKS)
 endif ()
 MARK_AS_ADVANCED (HDF5_STRICT_FORMAT_CHECKS)
 
-# ----------------------------------------------------------------------
-# Decide whether the data accuracy has higher priority during data
-# conversions.  If not, some hard conversions will still be preferred even
-# though the data may be wrong (for example, some compilers don't
-# support denormalized floating values) to maximize speed.
-#-----------------------------------------------------------------------------
-option (HDF5_WANT_DATA_ACCURACY "IF data accuracy is guaranteed during data conversions" ON)
-mark_as_advanced (HDF5_WANT_DATA_ACCURACY)
-if (HDF5_WANT_DATA_ACCURACY)
-  set (${HDF_PREFIX}_WANT_DATA_ACCURACY 1)
-endif ()
-MARK_AS_ADVANCED (HDF5_WANT_DATA_ACCURACY)
-
 # ----------------------------------------------------------------------
 # Decide whether the presence of user's exception handling functions is
 # checked and data conversion exceptions are returned.  This is mainly
@@ -871,83 +858,3 @@ if (HDF5_BUILD_FORTRAN)
   message (STATUS "maximum decimal precision for C var - ${${HDF_PREFIX}_PAC_C_MAX_REAL_PRECISION}")
 
 endif()
-
-#-----------------------------------------------------------------------------
-# Macro to determine the various conversion capabilities
-#-----------------------------------------------------------------------------
-macro (H5ConversionTests TEST msg)
-  if (NOT DEFINED ${TEST})
-    TRY_RUN (${TEST}_RUN   ${TEST}_COMPILE
-        ${CMAKE_BINARY_DIR}
-        ${HDF_RESOURCES_DIR}/ConversionTests.c
-        CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=-D${TEST}_TEST
-        OUTPUT_VARIABLE OUTPUT
-    )
-    if (${TEST}_COMPILE)
-      if (${TEST}_RUN EQUAL "0")
-        set (${TEST} 1 CACHE INTERNAL ${msg})
-        message (VERBOSE "${msg}... yes")
-      else ()
-        set (${TEST} "" CACHE INTERNAL ${msg})
-        message (VERBOSE "${msg}... no")
-        file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
-              "Test ${TEST} Run failed with the following output and exit code:\n ${OUTPUT}\n"
-        )
-      endif ()
-    else ()
-      set (${TEST} "" CACHE INTERNAL ${msg})
-      message (VERBOSE "${msg}... no")
-      file (APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
-          "Test ${TEST} Compile failed with the following output:\n ${OUTPUT}\n"
-      )
-    endif ()
-
-  endif ()
-endmacro ()
-
-#-----------------------------------------------------------------------------
-# Check various conversion capabilities
-#-----------------------------------------------------------------------------
-
-# ----------------------------------------------------------------------
-# Set the flag to indicate that the machine is using a special algorithm to convert
-# 'long double' to '(unsigned) long' values.  (This flag should only be set for
-# the IBM Power6 Linux.  When the bit sequence of long double is
-# 0x4351ccf385ebc8a0bfcc2a3c3d855620, the converted value of (unsigned)long
-# is 0x004733ce17af227f, not the same as the library's conversion to 0x004733ce17af2282.
-# The machine's conversion gets the correct value.  We define the macro and disable
-# this kind of test until we figure out what algorithm they use.
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_LDOUBLE_TO_LONG_SPECIAL  "Checking IF your system converts long double to (unsigned) long values with special algorithm")
-# ----------------------------------------------------------------------
-# Set the flag to indicate that the machine is using a special algorithm
-# to convert some values of '(unsigned) long' to 'long double' values.
-# (This flag should be off for all machines, except for IBM Power6 Linux,
-# when the bit sequences are 003fff..., 007fff..., 00ffff..., 01ffff...,
-# ..., 7fffff..., the compiler uses a unknown algorithm.  We define a
-# macro and skip the test for now until we know about the algorithm.
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_LONG_TO_LDOUBLE_SPECIAL "Checking IF your system can convert (unsigned) long to long double values with special algorithm")
-# ----------------------------------------------------------------------
-# Set the flag to indicate that the machine can accurately convert
-# 'long double' to '(unsigned) long long' values.  (This flag should be set for
-# all machines, except for Mac OS 10.4 and SGI IRIX64 6.5.  When the bit sequence
-# of long double is 0x4351ccf385ebc8a0bfcc2a3c..., the values of (unsigned)long long
-# start to go wrong on these two machines.  Adjusting it higher to
-# 0x4351ccf385ebc8a0dfcc... or 0x4351ccf385ebc8a0ffcc... will make the converted
-# values wildly wrong.  This test detects this wrong behavior and disable the test.
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_LDOUBLE_TO_LLONG_ACCURATE "Checking IF correctly converting long double to (unsigned) long long values")
-# ----------------------------------------------------------------------
-# Set the flag to indicate that the machine can accurately convert
-# '(unsigned) long long' to 'long double' values.  (This flag should be set for
-# all machines, except for Mac OS 10.4, when the bit sequences are 003fff...,
-# 007fff..., 00ffff..., 01ffff..., ..., 7fffff..., the converted values are twice
-# as big as they should be.
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_LLONG_TO_LDOUBLE_CORRECT "Checking IF correctly converting (unsigned) long long to long double values")
-# ----------------------------------------------------------------------
-# Set the flag to indicate that the machine can accurately convert
-# some long double values
-#-----------------------------------------------------------------------------
-H5ConversionTests (${HDF_PREFIX}_DISABLE_SOME_LDOUBLE_CONV "Checking IF the cpu is power9 and cannot correctly converting long double values")