* lto.c (hash_canonical_type): Use tree_code_for_canonical_type_merging.

	* tree.h (tree_code_for_canonical_type_merging): New function.
	* tree.c (gimple_canonical_types_compatible_p): Use
	tree_code_for_canonical_type_merging..
	* gcc.dg/lto/c-compatible-types_0.c: New testcase.
	* gcc.dg/lto/c-compatible-types_1.c: New testcase.

From-SVN: r224135