Implement alternate "__intN__" form of "__intN" type

Implement alternate "__intN__" form of "__intN" type

gcc/ChangeLog:

	* gcc/c-family/c-common.c (c_common_nodes_and_builtins): Define
	alternate "__intN__" name for "__intN" types.
	* gcc/c/c-parser.c (c_parse_init): Create keyword for "__intN__" type.
	* gcc/cp/lex.c (init_reswords): Likewise.
	* gcc/config/msp430/msp430.h: Use __int20__ for SIZE_TYPE and
	PTRDIFF_TYPE.
	* gcc/cp/cp-tree.h (cp_decl_specifier_seq): New bitfield "int_n_alt".
	* gcc/c/c-decl.c (declspecs_add_type): Don't pedwarn about "__intN" ISO
	C incompatibility if alternate "__intN__" form is used.
	* gcc/cp/decl.c (grokdeclarator): Likewise.
	* gcc/cp/parser.c (cp_parser_simple_type_specifier): Set
	decl_specs->int_n_alt if "__intN__" form is used.
	* gcc/gimple-ssa-sprintf.c (build_intmax_type_nodes): Accept "__intN__"
	format of "__intN" types for UINTMAX_TYPE.
	* gcc/brig/brig-lang.c (brig_build_c_type_nodes): Accept "__intN__"
	format of "__intN" types for SIZE_TYPE.
	* gcc/lto/lto-lang.c (lto_build_c_type_nodes): Likewise.
	* gcc/stor-layout.c (initialize_sizetypes): Accept "__intN__"
	format of "__intN" types for SIZETYPE.
	* gcc/tree.c (build_common_tree_nodes): Accept "__intN__"
	format of "__intN" types for SIZE_TYPE and PTRDIFF_TYPE.
	* gcc/doc/invoke.texi: Document that __intN__ disables pedantic
	warnings.

gcc/testsuite/ChangeLog:

	* gcc.target/msp430/mlarge-pedwarns.c: New test.

From-SVN: r272640