* config/tc-arm.c (arm_ext_v6m): New variable.

	* config/tc-arm.c (arm_ext_v6m): New variable.
	(arm_ext_m): Add support for OS extension.
	(arm_ext_os): New variable.
	(do_t_swi): In v6-M ensure we have the OS extension.
	(arm_cpus): The cortex-m1 and cortex-m0 options have the OS
	extension by default.
	(arm_archs): Add armv6s-m.
	(arm_extensions): Add 'os' extension.
	(cpu_arch_ver): Add support for v6S-M.
	* gas/doc/c-arm.texi: Document the OS Extension, and v6-m and v6s-m
	architecture options.
	* gas/testsuite/gas/arm/archv6s-m-bad.d: New test.
	* gas/testsuite/gas/arm/archv6s-m-bad.l: Likewise.
	* gas/testsuite/gas/arm/archv6s-m.d: Likewise.
	* gas/testsuite/gas/arm/archv6s-m.s: Likewise.
	* gas/testsuite/gas/arm/attr-march-armv6-m+os.d: Likewise.
	* gas/testsuite/gas/arm/attr-march-armv6s-m.d: Likewise.
	* include/opcode/arm.h (ARM_EXT_OS): New define.
	(ARM_AEXT_V6SM): Likewise.
	(ARM_ARCH_V6SM): Likewise.