[Erlang] Fix quoted identifier lookahead

Fixes sublimehq#1878 (comment)

This commit improves the quoted identifier pattern as the old one
caused the namespace lookahead to be triggered in the wrong place.

The following token was matched by the (?={{ident}}\s*:[^:=]) pattern
in the namespace context by accident:

   '$get_stacktrace') catch exit:'$get_stacktrace':

The new pattern makes sure to stop matching at the first unescaped
single quote. Any number of escaped backslashes is allowed in front of
it.

Erlang/Erlang.sublime-syntax

@@ -33,12 +33,15 @@ variables:
   # end of identifier lookahead
   # Note: avoid negative lookahead as it is 6-8% slower
   ident_break: (?={{ident_break_char}})
+  # a quoted identifier with possibly escaped single quote
+  # preceeded by an arbitary number of excaped backslashes
+  ident_quoted: \'((?:\\\\)*\\\'|[^''])*\'
   # an identifier can be an atom or a variable
   ident_unquoted: '[_A-Za-z]{{ident_char}}*'
   # all characters not being used to indicate a context change
   illegal_ident: '[^\s,:.;''(){}\[\]%=|/]+'
   # quoted/unquoted/macro identifier
-  ident: \?{,2}(?:{{ident_unquoted}}|\'.*?(?=[^\\])\')
+  ident: \?{,2}(?:{{ident_unquoted}}|{{ident_quoted}})
 
   # http://erlang.org/doc/reference_manual/macros.html#predefined-macros
   erlang_macros: |-

Erlang/syntax_test_erlang.erl

@@ -1630,6 +1630,34 @@ preprocessor_define_tests() -> .
 % <- punctuation.section.arguments.end.erlang
 %^ punctuation.terminator.clause.erlang
 
+-define(_get_stacktrace_(),
+        try exit('$get_stacktrace') catch exit:'$get_stacktrace':Stacktrace -> Stacktrace end).
+%       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ meta.preprocessor.define.arguments.erlang
+%       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ meta.exception.try.erlang
+%                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ meta.exception.catch.erlang
+%                                                                                         ^^^ meta.exception.try.erlang
+%           ^^^^ meta.function-call.name.erlang
+%               ^^^^^^^^^^^^^^^^^^^ meta.function-call.arguments.erlang
+%       ^^^ keyword.control.exception.try.erlang
+%           ^^^^ support.function.erlang
+%               ^ punctuation.section.arguments.begin.erlang
+%                ^ punctuation.definition.atom.begin.erlang
+%                ^^^^^^^^^^^^^^^^^ constant.other.symbol.erlang
+%                                ^ punctuation.definition.atom.end.erlang
+%                                 ^ punctuation.section.arguments.end.erlang
+%                                   ^^^^^ keyword.control.exception.catch.erlang
+%                                         ^^^^ constant.language.exception.type.erlang
+%                                             ^ punctuation.separator.patterns.erlang
+%                                              ^ punctuation.definition.atom.begin.erlang
+%                                              ^^^^^^^^^^^^^^^^^ constant.other.symbol.erlang
+%                                                              ^ punctuation.definition.atom.end.erlang
+%                                                               ^ punctuation.separator.patterns.erlang
+%                                                                ^^^^^^^^^^ variable.other.erlang
+%                                                                           ^^ punctuation.separator.clause-head-body.erlang
+%                                                                              ^^^^^^^^^^ variable.other.erlang
+%                                                                                         ^^^ keyword.control.exception.end.erlang
+%           
+
 % directive-export tests
 
 preprocessor_export_tests() -> .