Make wide-volatile loads and stores atomic.

This implements the four wide-volatile instructions added in a previous
change, and modifies the verifier to substitute the opcodes into the
instruction stream when appropriate.

For mterp, the ARM wide get/put instructions now have conditional code
that replaces ldrd/strd with a call to the quasiatomic functions.  The
C version does essentially the same thing.  ARMv4T lacks ldrd/stdrd, and
uses separate implementations for the wide field accesses, so those were
updated as well.  x86 will just use stubs.

The JIT should punt these to the interpreter.

Change-Id: Ife88559ed1a698c3267d43c454896f6b12081c0f
Also:
 - We don't seem to be using the negative widths in the instruction
   table.  Not sure they're useful anymore.
 - Tabs -> spaces in x86-atom throw-verification-error impl.