Allow extension availability to depend on several architecture bits

2016-05-10  Thomas Preud'homme  <thomas.preudhomme@arm.com>

gas/
	* config/tc-arm.c (struct arm_option_extension_value_table): Make
	allowed_archs an array with 2 entries.
	(ARM_EXT_OPT): Adapt to only fill the first entry of allowed_archs.
	(ARM_EXT_OPT2): New macro filling the two entries of allowed_archs.
	(arm_extensions): Use separate entries in allowed_archs when several
	archs are allowed to use an extension and change ARCH_ANY in
	ARM_ARCH_NONE in allowed_archs.
	(arm_parse_extension): Check that, for each allowed_archs entry, all
	bits are set in the current architecture, ignoring ARM_ANY entries.
	(s_arm_arch_extension): Likewise.

include/
	* arm.h (ARM_FSET_CPU_SUBSET): Define macro.