gccrs: Replace TOK suffix with KW

gccrs: Replace TOK suffix with KW

TOK suffix was chosen to disambiguate some identifiers with c++ reserved
keyword. Even though this list lies within the rust-token header, this
macro is used in many context sometimes unrelated with the lexer and
tokens. This TOK suffix may appear surprising in such context.

gcc/rust/ChangeLog:

	* lex/rust-token.h (enum PrimitiveCoreType): Change keyword suffix from
	tok to kw.
	* ast/rust-ast-collector.cc (TokenCollector::visit): Update suffix to
	match the new declaration.
	* lex/rust-lex.cc (Lexer::parse_raw_identifier): Likewise.
	* parse/rust-parse-impl.h (can_tok_start_type): Likewise.
	(Parser::parse_item): Likewise.
	(Parser::parse_vis_item): Likewise.
	(Parser::parse_extern_crate): Likewise.
	(Parser::parse_function): Likewise.
	(Parser::parse_function_qualifiers): Likewise.
	(Parser::parse_struct): Likewise.
	(Parser::parse_enum): Likewise.
	(Parser::parse_static_item): Likewise.
	(Parser::parse_trait_item): Likewise.
	(Parser::parse_inherent_impl_item): Likewise.
	(Parser::parse_trait_impl_item): Likewise.
	(Parser::parse_extern_block): Likewise.
	(Parser::parse_external_item): Likewise.
	(Parser::parse_stmt): Likewise.
	(Parser::parse_return_expr): Likewise.
	(Parser::parse_match_expr): Likewise.
	(Parser::parse_type): Likewise.
	(Parser::parse_for_prefixed_type): Likewise.
	(Parser::parse_type_no_bounds): Likewise.
	(Parser::parse_stmt_or_expr): Likewise.
	* parse/rust-parse.cc (peculiar_fragment_match_compatible): Likewie.
	* util/rust-token-converter.cc (convert): Likewise.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>