Fix PR16193 - gdbserver aborts.

Fix PR16193 - gdbserver aborts.

The MPX patch has broken the I386_XSTATE_SIZE macro.  For AVX machines,
it ends up returning I386_XSTATE_SSE_SIZE.  Where it first reads
I386_XSTATE_AVX_SIZE, it should have read I386_XSTATE_AVX:

 #define I386_XSTATE_SIZE(XCR0) \
     (((XCR0) & I386_XSTATE_BNDCFG) != 0 ? I386_XSTATE_BNDCFG_SIZE \
        : (((XCR0) & I386_XSTATE_BNDREGS) != 0 ? I386_XSTATE_BNDCFG_SIZE \
 -       : (((XCR0) & I386_XSTATE_AVX_SIZE) != 0 ? I386_XSTATE_AVX_SIZE \
 +       : (((XCR0) & I386_XSTATE_AVX) != 0 ? I386_XSTATE_AVX_SIZE \
        : I386_XSTATE_SSE_SIZE)))

The patch goes a step further and improves readability of the macro,
by adding a couple other auxiliary macros.

2013-11-26  Walfred Tedeschi  <walfred.tedeschi@intel.com>

	* i386-xstate.h (I386_XSTATE_MPX): New Macro.
	(I386_XSTATE_MPX_MASK): Makes use of I386_XSTATE_MPX.
	(HAS_MPX): New macro.
	(HAS_AVX): New macro.
	(I386_XSTATE_SIZE): Uses HAS_MPX and HAS_AVX.