Patched the lexer to not re-define RETURN.

Hi!

  The gcc-2.95.3 sources do not compile under gcc-4.4, the error given is the following:

In file included from m68k-amigaos-toolchain/sources/gcc-2.95.3/gcc/c-lex.c:31:
m68k-amigaos-toolchain/sources/gcc-2.95.3/gcc/c-parse.h:64:error: redeclaration of enumerator 'RETURN'
m68k-amigaos-toolchain/sources/gcc-2.95.3/gcc/rtl.def:503: note: previous definition of 'RETURN' was here

and stems from the fact that "RETURN" is defined twice from the files included by "c-lex.c":

- in "c-parse.h"
- from "rtl.h" and thereby "rtl.def"

which both contain a definition for "RETURN".

"c-lex.c" does not need "rtl.h" included (in fact, you can remove "rtl.h" entirely), however, to maintain the original source, I have created a patch that avoids the double-definition by inclusion of "rtl.h":

The patch is located at patches/gcc-2.95.3/gcc/c-lex.c.diff and refuses to include "rtl.h" in case it has already been defined by "c-parse.h":

#ifndef RETURN
#include "rtl.h"
#endif

If useful, please commit. Thanks.