Relax cgraph_node::clone_of_p to also look through former clones

Relax cgraph_node::clone_of_p to also look through former clones

2019-03-07  Martin Jambor  <mjambor@suse.cz>

	PR ipa/88235
	* cgraph.h (cgraph_node): New inline method former_thunk_p.
	* cgraph.c (cgraph_node::dump): Dump a note if node is a former thunk.
	(clone_of_p): Treat expanded thunks like thunks, be optimistic if they
	have multiple callees.  At the end check if declarations match as
	opposed to cgraph_nodes.

	testsuite/
	* g++.dg/ipa/pr88235.C: New test.

From-SVN: r269462