Add effective target signal

Add effective target signal

2017-06-10  Tom de Vries  <tom@codesourcery.com>

	* lib/target-supports.exp (check_effective_target_signal): New proc.
	* lib/gcc.exp (gcc_target_compile): Remove appending of
	-DSIGNAL_SUPPRESS to additional_flags.
	* gcc.c-torture/execute/ieee/ieee.exp: Add -DSIGNAL_SUPPRESS to
	additional_flags if effective target signal is not supported by the
	target.
	* gcc.c-torture/execute/20101011-1.c: Same.
	* gcc.dg/c99-stdint-1.c: Same.
	* gcc.dg/c99-stdint-2.c: Same.
	* gcc.dg/c99-stdint-5.c: Same.
	* gcc.dg/c99-stdint-6.c: Same.
	* gcc.dg/stdint-width-1.c: Same.

	* doc/sourcebuild.texi (Effective-Target Keywords, Environment
	attributes): Document signal effective target.

From-SVN: r249091