[PATCH] Fix preprocessor expansion anti-recursion properly

[PATCH] Fix preprocessor expansion anti-recursion properly

We taint identifiers when we are done with argument expansion; we
untaint them when scan gets through the "untaint" token we leave right
after the body of macro; we mark tokens noexpand in three situations:
	1) when we copy a token marked noexpand;
	2) when we get to expanding a token and see that its identifier is
currently tainted;
	3) when we scan for closing ) and see an identifier token with
currently tainted identifier.

That makes sure that by the time we get past the expanded body (and
untaint the left-hand side of macro), all tokens bearing that identifier
will be seen and marked noexpand.

There is more elegant variant (it's practically straight from text of
standard - set noexpand only in dup_token() and make it
	if (token_type(token) == TOKEN_IDENT)
		alloc->noexpand = token->noexpand | token->ident->tainted;
which is as close as to transliteration of 6.10.3.4(2) as it gets), but
before we can go for it, we need to sort out another problem - order of
expansion/copying for arguments.

So for now here's an equivalent heavier variant with a wart ((3) above)
that works even with current expand_arguments() and when that gets sorted
out we'll be able to get anti-recursion logics absolutely straightforward.

And yes, it does preprocessor1.c correctly; it even get much subtler
preprocessor7.c right.