Check for warning flags without no- prefix

config/:
	PR bootstrap/51388
	* warnings.m4 (ACX_PROG_CC_WARNING_OPTS)
	(ACX_PROG_CC_WARNING_ALMOST_PEDANTIC): Run the test without the
	no- prefix.
fixincludes/:
	* configure: Regenerate.
gcc/:
	* configure: Regenerate.
libcpp/:
	* configure: Regenerate.
libdecnumber/:
	* configure: Regenerate.
libiberty/:
	* configure: Regenerate.
lto-plugin/:
	* configure: Regenerate.

From-SVN: r182478