mesa: Remove last BEOS checks

* Goodbye BeOS, we hardly knew thee
* As BeOS was gcc2 only, there was little chance
  of this being useful.
* Doesn't effect Haiku in any meaningful way

Reviewed-by: Brian Paul <brianp@vmware.com>

include/GL/gl.h

@@ -36,10 +36,6 @@
  * Begin system-specific stuff.
  */
 
-#if defined(__BEOS__)
-#include <stdlib.h>     /* to get some BeOS-isms */
-#endif
-
 #if defined(_WIN32) && !defined(__WIN32__) && !defined(__CYGWIN__)
 #define __WIN32__
 #endif
@@ -65,10 +61,6 @@
 #  define GLAPIENTRY
 #endif /* WIN32 && !CYGWIN */
 
-#if (defined(__BEOS__) && defined(__POWERPC__))
-#  define PRAGMA_EXPORT_SUPPORTED		1
-#endif
-
 /*
  * WINDOWS: Include windows.h here to define APIENTRY.
  * It is also useful when applications include this file by

scons/gallium.py

@@ -295,8 +295,6 @@ def generate(env):
             cppdefines += ['_DEBUG']
     if platform == 'windows':
         cppdefines += ['PIPE_SUBSYSTEM_WINDOWS_USER']
-    if platform == 'haiku':
-        cppdefines += ['BEOS_THREADS']
     if env['embedded']:
         cppdefines += ['PIPE_SUBSYSTEM_EMBEDDED']
     if env['texture_float']: