fix-header.c (enum special_file): Undefine enumerators if they are already defined by include files.

a
	* fix-header.c (enum special_file): Undefine enumerators if they
	are already defined by include files.
	* fixproto (rel_source_file in unistd.h stdlib.h): Prefix file protection
	macro with '__' to not pollute user namespace.

From-SVN: r19298