c-family, c++: Look up built-in traits via identifier node

c-family, c++: Look up built-in traits via identifier node

Since RID_MAX soon reaches 255 and all built-in traits are used
approximately once in a C++ translation unit, this patch removes
all RID values for built-in traits and uses the identifier node to
look up the specific trait.  Rather than holding traits as keywords,
we set all trait identifiers as cik_trait, which is a new
cp_identifier_kind.  As cik_reserved_for_udlit was unused and
cp_identifier_kind is 3 bits, we replaced the unused field with the new
cik_trait.  Also, the later patch handles a subsequent token to the
built-in identifier so that we accept the use of non-function-like
built-in trait identifiers.

gcc/c-family/ChangeLog:

	* c-common.cc (c_common_reswords): Remove all mappings of
	built-in traits.
	* c-common.h (enum rid): Remove all RID values for built-in
	traits.

gcc/cp/ChangeLog:

	* cp-objcp-common.cc (names_builtin_p): Remove all RID value
	cases for built-in traits.  Check for built-in traits via
	the new cik_trait kind.
	* cp-tree.h (enum cp_trait_kind): Set its underlying type to
	addr_space_t.
	(struct cp_trait): New struct to hold trait information.
	(cp_traits): New array to hold a mapping to all traits.
	(cik_reserved_for_udlit): Rename to ...
	(cik_trait): ... this.
	(IDENTIFIER_ANY_OP_P): Exclude cik_trait.
	(IDENTIFIER_TRAIT_P): New macro to detect cik_trait.
	* lex.cc (cp_traits): Define its values, declared in cp-tree.h.
	(init_cp_traits): New function to set cik_trait and
	IDENTIFIER_CP_INDEX for all built-in trait identifiers.
	(cxx_init): Call init_cp_traits function.
	* parser.cc (cp_lexer_lookup_trait): New function to look up a
	built-in trait by IDENTIFIER_CP_INDEX.
	(cp_lexer_lookup_trait_expr): Likewise, look up an
	expression-yielding built-in trait.
	(cp_lexer_lookup_trait_type): Likewise, look up a type-yielding
	built-in trait.
	(cp_keyword_starts_decl_specifier_p): Remove all RID value cases
	for built-in traits.
	(cp_lexer_next_token_is_decl_specifier_keyword): Handle
	type-yielding built-in traits.
	(cp_parser_primary_expression): Remove all RID value cases for
	built-in traits.  Handle expression-yielding built-in traits.
	(cp_parser_trait): Handle cp_trait instead of enum rid.
	(cp_parser_simple_type_specifier): Remove all RID value cases
	for built-in traits.  Handle type-yielding built-in traits.

Co-authored-by: Patrick Palka <ppalka@redhat.com>
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>