Unsigned constants for ISO_FORTRAN_ENV and ISO_C_BINDING.

gcc/fortran/ChangeLog:

	* dump-parse-tree.cc (get_c_type_name): Also handle BT_UNSIGNED.
	* gfortran.h (NAMED_UINTCST): Define before inclusion
	of iso-c-binding.def and iso-fortran-env.def.
	(gfc_get_uint_kind_from_width_isofortranenv): Prototype.
	* gfortran.texi: Mention new constants in iso_c_binding and
	iso_fortran_env.
	* iso-c-binding.def: Handle NAMED_UINTCST. Add c_unsigned,
	c_unsigned_short,c_unsigned_char, c_unsigned_long,
	c_unsigned_long_long, c_uintmax_t, c_uint8_t, c_uint16_t,
	c_uint32_t, c_uint64_t, c_uint128_t, c_uint_least8_t,
	c_uint_least16_t, c_uint_least32_t, c_uint_least64_t,
	c_uint_least128_t, c_uint_fast8_t, c_uint_fast16_t,
	c_uint_fast32_t, c_uint_fast64_t and c_uint_fast128_t.
	* iso-fortran-env.def: Handle NAMED_UINTCST. Add uint8, uint16,
	uint32 and uint64.
	* module.cc (parse_integer): Whitespace fix.
	(write_module): Whitespace fix.
	(NAMED_UINTCST): Define before inclusion of iso-fortran-evn.def
	and iso-fortran-env.def.
	* symbol.cc: Likewise.
	* trans-types.cc (get_unsigned_kind_from_node): New function.
	(get_uint_kind_from_name): New function.
	(gfc_get_uint_kind_from_width_isofortranenv): New function.
	(get_uint_kind_from_width): New function.
	(gfc_init_kinds): Initialize gfc_c_uint_kind.

gcc/testsuite/ChangeLog:

	* gfortran.dg/unsigned_36.f90: New test.