[PR c/84293] Unexpected strict-alias warning

[PR c/84293] Unexpected strict-alias warning

https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00510.html
	PR c/84293
	gcc/c/
	* c-typeck.c (build_indirect_ref, build_c_cast): Pass expr location
	to strict_aliasing_warning.

	gcc/c-family/
	* c-common.h (strict_aliasing_warning): Drop OTYPE arg, insert LOC
	arg.
	* c-warn.c (strict_aliasing_warning): Drop OTYPE arg, require LOC
	arg.  Adjust.

	gcc/cp/
	* typeck.c (cp_build_indirect_ref_1, build_reinterpret_cast_1):
	Pass expr location to strict_aliasing_warning.

	gcc/testsuite/
	* c-c++-common/pr84293.h: New.
	* c-c++-common/pr84293.c: New.

From-SVN: r257539