* gas/config/tc-arm.c (arm_cpu_option_table): Add name_len field.

	(arm_arch_option_table): Likewise.
	(arm_option_extension_value_table): Likewise.
	(ARM_CPU_OPT): New define.
	(ARM_ARCH_OPT): Likewise.
	(ARM_EXT_OPT): Likewise.
	(arm_cpus): Use ARM_CPU_OPT to initialize.
	(arm_archs): Use ARM_ARCH_OPT to initialize.
	(arm_extensions): Use ARM_EXT_OPT to initialize.
	(arm_parse_extension): Ensure option string matching matches
	the whole string.
	(arm_parse_cpu): Likewise.
	(arm_parse_arch): Likewise.
	* gas/testsuite/gas/arm/cmdline-bad-arch.d: New test case.
	* gas/testsuite/gas/arm/cmdline-bad-cpu.d: Likewise.