gl_table.py: add extern C guard for the generated glapitable.h

The header can be included from C++, hence contents should have
appropriate notation.

Cc: mesa-stable@lists.freedesktop.org
Cc: Dylan Baker <dylan@pnwbakers.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

src/mapi/glapi/gen/gl_table.py

@@ -58,12 +58,20 @@ class PrintGlTable(gl_XML.gl_print_base):
         print '#endif'
         print ''
         print ''
+        print '#ifdef __cplusplus'
+        print 'extern "C" {'
+        print '#endif'
+        print ''
         print 'struct _glapi_table'
         print '{'
         return
 
     def printRealFooter(self):
         print '};'
+        print ''
+        print '#ifdef __cplusplus'
+        print '}'
+        print '#endif'
         return