PR c/81854 - weak alias of an incompatible symbol accepted

PR c/81854 - weak alias of an incompatible symbol accepted

gcc/ChangeLog:

	PR c/81854
	* cgraphunit.c (handle_alias_pairs): Reject aliases between functions
	of incompatible types.

gcc/testsuite/ChangeLog:

	PR c/81854
	* gcc.dg/pr81854.c: New test.
	* g++.dg/ext/attr-ifunc-5.C: New test.
	* g++.dg/ext/attr-ifunc-1.C: Adjust.
	* g++.dg/ext/attr-ifunc-2.C: Same.
	* g++.dg/ext/attr-ifunc-3.C: Same.
	* g++.dg/ext/attr-ifunc-4.C: Same.
	* g++.old-deja/g++.abi/vtable2.C: Same.
	* gcc.dg/attr-ifunc-1.c: Same.

From-SVN: r252976