* Keep track of register alignment as well as register size

* Keep track of register alignment as well as register size
* Add comments
* Add a new allocation_order iterator for register classes which targets may
  use to control the register order and available registers based on properties
  of the function being compiled.
* Remove access to FP and SP registers
* Add new callframe setup opcode support
* Eliminate moveImm2Reg method
* Revamp frame offset handling and prolog/epilog code generation

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5167 91177308-0d34-0410-b5e6-96231b3b80d8