The PE targets don't support mapping symbols and so the disassembler is unable
to correctly output thumb instructions when the input was thumb.

So for testcases that only have thumb output, I have copied them and skipped the
ones for which auto-detection is supposed to work on PE, and added a new one
that will force thumb output.  This so that the tests still check the mapping
symbols.

For the tests that switch between thumb and arm in one file I just skip them
entirely on PE targets.

This cleans up the PE GAS testsuite.

gas/

	* testsuite/gas/arm/archv6t2-1-pe.d: New test.
	* testsuite/gas/arm/archv6t2-1.d: Skip pe.
	* testsuite/gas/arm/csdb.d: Skip pe.
	* testsuite/gas/arm/sb-thumb1-pe.d: New test.
	* testsuite/gas/arm/sb-thumb1.d: Skip pe.
	* testsuite/gas/arm/sb-thumb2-pe.d: New test.
	* testsuite/gas/arm/sb-thumb2.d: Skip pe.
	* testsuite/gas/arm/udf.d: Skip pe.

Implement the assembly instructions yield, wfe, wfi and sev for ARMv6T2 in both ARM mode and Thumb mode.

	* config/tc-arm.c (arm_ext_v6k_v6t2): Define.
	(insns) [ARM_VARIANT]: Modified.
	(insns) [THUMB_VARIANT]: To implement few ARMv6K instructions
	in ARMv6T2 as well.
	* testsuite/gas/arm/archv6t2-1.d: New test.
	* testsuite/gas/arm/archv6t2-1.s: Likewise.
	* testsuite/gas/arm/archv6t2-2.d: Likewise.