c-common.c (maybe_warn_shift_overflow): Warn on all overflows if shifting 1 out of...

c-common.c (maybe_warn_shift_overflow): Warn on all overflows if shifting 1 out of the sign bit.

gcc:
2015-12-04  Paolo Bonzini  <bonzini@gnu.org>

	* c-family/c-common.c (maybe_warn_shift_overflow): Warn on all
	overflows if shifting 1 out of the sign bit.

gcc/testsuite:
2015-12-04  Paolo Bonzini  <bonzini@gnu.org>

	* c-c++-common/Wshift-overflow-1.c: Test shifting 1 out of the sign bit.
	* c-c++-common/Wshift-overflow-2.c: Test shifting 1 out of the sign bit.
	* c-c++-common/Wshift-overflow-3.c: Test shifting 1 out of the sign bit.
	* c-c++-common/Wshift-overflow-4.c: Test shifting 1 out of the sign bit.
	* c-c++-common/Wshift-overflow-6.c: Test shifting 1 out of the sign bit.
	* c-c++-common/Wshift-overflow-7.c: Test shifting 1 out of the sign bit.

From-SVN: r231290