re PR c++/44609 (Invalid template code causes infinite loop of error messages)

re PR c++/44609 (Invalid template code causes infinite loop of error messages)

	PR c++/44609
	* cp-tree.h (struct tinst_level): Add errors field.
	* pt.c (neglectable_inst_p, limit_bad_template_recurson): New.
	(push_tinst_level): Don't start another decl in that case.
	(reopen_tinst_level): Adjust errors field.
	* decl2.c (cp_write_global_declarations): Don't complain about
	undefined inline if its template was defined.
	* mangle.c (mangle_decl_string): Handle failure from push_tinst_level.

From-SVN: r176176