c++: improve debug_tree for templated types/decls

gcc/cp/ChangeLog:

	* ptree.cc (cxx_print_decl): Check for DECL_LANG_SPECIFIC and
	TS_DECL_COMMON only when necessary.  Print DECL_TEMPLATE_INFO
	for all decls that have it, not just VAR_DECL or FUNCTION_DECL.
	Also print DECL_USE_TEMPLATE.
	(cxx_print_type): Print TYPE_TEMPLATE_INFO.
	<case BOUND_TEMPLATE_TEMPLATE_PARM>: Don't print TYPE_TI_ARGS
	anymore.
	<case TEMPLATE_TYPE/TEMPLATE_PARM>: Print TEMPLATE_TYPE_PARM_INDEX
	instead of printing the index, level and original level
	individually.