re PR c++/61623 (ICE: verify_symtab failed: Two symbols with same comdat_group are not linked by the same_comdat_group list.)

	PR c++/61623
	* symtab.c (symtab_remove_from_same_comdat_group): Also
	set_comdat_group to NULL_TREE.
	(verify_symtab): Fix diagnostic.

From-SVN: r212705