Use RegisterTuples to generate pseudo-registers.

Use RegisterTuples to generate pseudo-registers.

The QQ and QQQQ registers are not 'real', they are pseudo-registers used
to model some vld and vst instructions.

This makes the call clobber lists longer, but I intend to get rid of
those soon.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148151 91177308-0d34-0410-b5e6-96231b3b80d8