Fix cmake build on windows. (#34214)

This fixes several minor issues:

- platform_win.h needs to be included before SDL stuff, otherwise
  you get seemingly unrelated errors. This happened to work in VS
  solution because it force-includes stdafx.h everywhere. However
  stdafx.h should only be used as an optimization measure, and not
  to guarantee correctness

- The binary currently does not use SDL2main helper, and instead
  defines all initialization in WinMain itself. I didn't try searching
  for the specific commit, but according to comments in Makefile,
  this is a deliberate change.
  VS solution defines USE_WINMAIN unconditionally, so let's use it
  in cmake as well.

- WinMain, as defined currently, has its arguments unused, which
  makes g++ complain, and fail due to -Werror.
  Removed the comments

- Mostly unrelated, and not strictly necessary: the "idiomatic"
  way to require a C++ standard in cmake is
  `SET(CMAKE_CXX_STANDARD 14)`, which is very slightly preferred over
  `SET(CMAKE_CXX_FLAGS -std=c++14)` due to cross-platform
  considerations.
  The option is present since at least CMake 3.1.3, released
  in february 2015. This is only 3 months later than C++14 release,
  so the version bump should not be problematic.

CMakeLists.txt

@@ -1,5 +1,5 @@
 # Main project build script
-cmake_minimum_required(VERSION 3.0.0)
+cmake_minimum_required(VERSION 3.1.4)
 
 PROJECT(CataclysmDDA)
 
@@ -225,10 +225,12 @@ ELSE()
 		-Wpedantic")
 	# Compact the whitespace in the warning string
 	string(REGEX REPLACE "[\t ]+" " " CATA_WARNINGS "${CATA_WARNINGS}")
-	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CATA_WARNINGS} -std=c++14")
+	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CATA_WARNINGS}")
 	SET(CMAKE_CXX_FLAGS_DEBUG "-Og -g")
 ENDIF()
 
+SET(CMAKE_CXX_STANDARD 14)
+
 # Force out-of-source build
 IF(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
 	MESSAGE(FATAL_ERROR

src/CMakeLists.txt

@@ -39,6 +39,7 @@ IF(TILES)
 	target_include_directories(libcataclysm-tiles INTERFACE ${CMAKE_SOURCE_DIR}/src)
 
 	IF(WIN32)
+		ADD_DEFINITIONS(-DUSE_WINMAIN)
 		ADD_EXECUTABLE(cataclysm-tiles WIN32
 			${MAIN_CPP}
 			${RESOURCE_RC}

src/main.cpp

@@ -123,7 +123,8 @@ void printHelpMessage( const arg_handler *first_pass_arguments, size_t num_first
 }  // namespace
 
 #if defined(USE_WINMAIN)
-int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
+int APIENTRY WinMain( HINSTANCE /* hInstance */, HINSTANCE /* hPrevInstance */,
+                      LPSTR /* lpCmdLine */, int /* nCmdShow */ )
 {
     int argc = __argc;
     char **argv = __argv;

src/sdltiles.cpp

@@ -22,6 +22,7 @@
 #include <type_traits>
 #include <tuple>
 
+#include "platform_win.h"
 #if defined(_MSC_VER) && defined(USE_VCPKG)
 #   include <SDL2/SDL_image.h>
 #   include <SDL2/SDL_syswm.h>