Use SDLCALL for callbacks in public APIs

include/SDL_config_os2.h

@@ -102,8 +102,11 @@
 #define HAVE_GETENV 1
 #define HAVE_SETENV 1
 #define HAVE_PUTENV 1
+/* OpenWatcom requires specific calling conventions for qsort and bsearch */
+#ifndef __WATCOMC__
 #define HAVE_QSORT 1
 #define HAVE_BSEARCH 1
+#endif
 #define HAVE_ABS 1
 #define HAVE_BCOPY 1
 #define HAVE_MEMSET 1