c-common.h (enum rid): Remove RID_IS_CONVERTIBLE_TO.

c-common.h (enum rid): Remove RID_IS_CONVERTIBLE_TO.

c-family/
	* c-common.h (enum rid): Remove RID_IS_CONVERTIBLE_TO.
	* c-common.c (c_common_reswords): Remove __is_convertible_to.
cp/
	* cp-tree.h (cp_trait_kind): Remove CPTK_IS_CONVERTIBLE_TO.
	* cxx-pretty-print.c (pp_cxx_trait_expression): Likewise.
	* semantics.c (trait_expr_value): Likewise.
	(finish_trait_expr): Likewise.
	* parser.c (cp_parser_primary_expression): Likewise.
	(cp_parser_trait_expr): Likewise. Remove redundant grokdeclarator.

From-SVN: r215735