Move _putenv and _wputenv out of _POSIX_ guard.

See http://msdn.microsoft.com/en-us/library/83zh4e6k.aspx
for more details.

mingw-w64-headers/crt/stdlib.h

diff --git a/mingw-w64-headers/crt/stdlib.h b/mingw-w64-headers/crt/stdlib.h
index 839cace..7743452 100644
--- a/mingw-w64-headers/crt/stdlib.h
+++ b/mingw-w64-headers/crt/stdlib.h
@@ -520,6 +520,9 @@
   __MINGW_EXTENSION _CRTIMP unsigned __int64 __cdecl _wcstoui64_l(const wchar_t *_Str ,wchar_t **_EndPtr,int _Radix,_locale_t _Locale);
 #endif
 
+  _CRTIMP int __cdecl _putenv(const char *_EnvString);
+  _CRTIMP int __cdecl _wputenv(const wchar_t *_EnvString);
+
 #ifndef _POSIX_
 #define _CVTBUFSIZE (309+40)
   _CRTIMP char *__cdecl _fullpath(char *_FullPath,const char *_Path,size_t _SizeInBytes);
@@ -553,7 +556,6 @@
 #define _CRT_PERROR_DEFINED
   void __cdecl perror(const char *_ErrMsg);
 #endif
-  _CRTIMP int __cdecl _putenv(const char *_EnvString);
 #pragma push_macro ("_rotr64")
 #pragma push_macro ("_rotl64")
 #undef _rotl64
@@ -583,7 +585,6 @@
 #define _CRT_WPERROR_DEFINED
   _CRTIMP void __cdecl _wperror(const wchar_t *_ErrMsg);
 #endif
-  _CRTIMP int __cdecl _wputenv(const wchar_t *_EnvString);
   _CRTIMP void __cdecl _wsearchenv(const wchar_t *_Filename,const wchar_t *_EnvVar,wchar_t *_ResultPath) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
   _CRTIMP void __cdecl _wsplitpath(const wchar_t *_FullPath,wchar_t *_Drive,wchar_t *_Dir,wchar_t *_Filename,wchar_t *_Ext) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
 #endif