- Add getParent() accessors.
  - Move SubReg out of the AuxInfo union, to make way for future changes.
  - Remove the getImmedValue/setImmedValue methods.
  - in some MachineOperand::Create* methods, stop initializing fields that are dead.

MachineInstr:
  - Delete one copy of the MachineInstr printing code, now there is only one dump
    format and one copy of the code.
  - Make MachineOperand use the parent field to get info about preg register names if
    no target info is otherwise available.
  - Move def/use/kill/dead flag printing to the machineoperand printer, so they are
    always printed for an operand.

llvm-svn: 45460