Make sure __inline__ isn't defined before #defining it, since some compilers

 (like Sun Studio) have this as a predefined macro.

   Fixes Bugzilla #434.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%402354

include/begin_code.h

@@ -123,7 +123,9 @@
 #define SDL_INLINE_OKAY
 #else
 #if !defined(__MRC__) && !defined(_SGI_SOURCE)
+#ifndef __inline__
 #define __inline__ inline
+#endif
 #define SDL_INLINE_OKAY
 #endif /* Not a funky compiler */
 #endif /* Visual C++ */