- Clean up tablegen dag isel generator code.

- Clean up tablegen dag isel generator code.
- Clean up the code generated by tablegen:
  * AddToISelQueue now takes one argument.
  * ComplexPattern matching condition can now be shared.
  * Eliminate passing unnecessary arguments to emit routines.
  * Eliminate some unneeded SDOperand declarations in select routines.
  * Other minor clean ups.
- This reduces foot print slightly: X86ISelDAGToDAG.o is reduced from 971k
  to 823k.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29892 91177308-0d34-0410-b5e6-96231b3b80d8