revision of skip_if_group

[Zack Weinberg]

This patch is a rewrite of the skip_if_group function.  By itself it
does little besides clarify the logic.  It was going to be part of a
larger patch that got rid of parse markers, but I'm getting bizarre
failures with that patch, and this part works.

[Why do I want to get rid of parse markers?  Because they interfere
with plans to get rid of lazy line counting, which is the #1
performance problem in cpplib.]

zw

1998-12-21 18:03 -0500  Zack Weinberg  <zack@rabi.phys.columbia.edu>

	* cpplib.c (skip_if_group): Split out the logic that handles
	directive recognition to its own function.  Don't use
	parse markers; use a bare pointer into the buffer.  Use
	copy/skip_rest_of_line instead of doing it by hand.  Remove
	`return on any directive' mode which was never used, and take
	only one argument.
	(consider_directive_while_skipping): New function, subroutine
	of skip_if_group.  Logic streamlined a bit.
	(conditional_skip, do_elif, do_else): Call skip_if_group with
	only one argument.