Refactor the code to emit multiple-inclusion protection to
FilterGLAPISpecBase.  Since the size_h mode of glX_proto_size.py will be
used to generate multiple header files, add an option to specify the define
that is used for multiple-inclusion protection.

The changes to the header files in this commit are just a side-effect of the
changes to the Python scripts.
diff --git a/src/mesa/glapi/gl_offsets.py b/src/mesa/glapi/gl_offsets.py
index 3ff27e7..f5bd7f4 100644
--- a/src/mesa/glapi/gl_offsets.py
+++ b/src/mesa/glapi/gl_offsets.py
@@ -38,6 +38,7 @@
 
 	def __init__(self):
 		gl_XML.FilterGLAPISpecBase.__init__(self)
+		self.header_tag = '_GLAPI_OFFSETS_H_'
 		self.license = license.bsd_license_template % ( \
 """Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
 (C) Copyright IBM Corporation 2004""", "BRIAN PAUL, IBM")
@@ -46,16 +47,6 @@
 		if f.fn_offset < 0: return
 		print '#define _gloffset_%s %d' % (f.name, f.fn_offset)
 
-	def printRealHeader(self):
-		print '#ifndef _GLAPI_OFFSETS_H_'
-		print '#define _GLAPI_OFFSETS_H_'
-		print ''
-		return
-
-	def printRealFooter(self):
-		print ''
-		print '#endif'
-		return
 
 def show_usage():
 	print "Usage: %s [-f input_file_name]" % sys.argv[0]