cp-tree.h (DECL_EXTERNAL_LINKAGE_P): New macro.

	* cp-tree.h (DECL_EXTERNAL_LINKAGE_P): New macro.
	(linkage_kind): New enumeration.
	(decl_linkage): New function.
	* decl2.c (comdat_linkage): Extend comment.
	* error.c (dump_function_decl): Print the arguments used to
	instantiate a template, even when not printing the type of the
	function.
	* pt.c (convert_nontype_argument): Use DECL_EXTERNAL_LINKAGE_P,
	not TREE_PUBLIC, to test for external linkage.
	* tree.c (decl_linkage): New function.

From-SVN: r37150