Removed outdated OS/2 support

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403810

include/begin_code.h

@@ -49,16 +49,6 @@
 #  else
 #   define DECLSPEC	__declspec(dllexport)
 #  endif
-# elif defined(__OS2__)
-#  ifdef __WATCOMC__
-#   ifdef BUILD_SDL
-#    define DECLSPEC	__declspec(dllexport)
-#   else
-#    define DECLSPEC
-#   endif
-#  else
-#   define DECLSPEC
-#  endif
 # else
 #  if defined(__GNUC__) && __GNUC__ >= 4
 #   define DECLSPEC	__attribute__ ((visibility("default")))
@@ -73,14 +63,8 @@
 #if defined(__WIN32__) && !defined(__GNUC__)
 #define SDLCALL __cdecl
 #else
-#ifdef __OS2__
-/* But on OS/2, we use the _System calling convention */
-/* to be compatible with every compiler */
-#define SDLCALL _System
-#else
 #define SDLCALL
 #endif
-#endif
 #endif /* SDLCALL */
 
 /* Removed DECLSPEC on Symbian OS because SDL cannot be a DLL in EPOC */