* c-common.c (format_check_results): New structure.
	(finish_dollar_format_checking): Adjust to take a
	format_check_results * parameter.
	(check_format_info, check_format_info_recurse,
	check_format_info_main): Split check_format_info into three
	functions, the main checking going in check_format_info_main.
	Recurse when any reduction of the format string argument towards a
	string literal is done; go down both branches of a conditional
	expression.  Don't warn for extra format arguments or empty format
	strings if they only occur in some branches of a conditional
	expression.

testsuite:
	* gcc.dg/format-branch-1.c: New test.

From-SVN: r36883