re PR c/58346 (ICE with SIGFPE at -O1 and above on x86_64-linux-gnu (affecting trunk, 4.8, 4.7, and 4.6))

	PR c/58346
c-family/
	* c-common.c (pointer_to_zero_sized_aggr_p): New function.
	* c-common.h: Declare it.
cp/
	* typeck.c (pointer_diff): Give an error on arithmetic on pointer to
	an empty aggregate.
c/
	* c-typeck.c (pointer_diff): Give an error on arithmetic on pointer to
	an empty aggregate.
testsuite/
	* c-c++-common/pr58346-1.c: New test.
	* c-c++-common/pr58346-2.c: New test.
	* c-c++-common/pr58346-3.c: New test.

From-SVN: r207004