This is a general clean up of the PowerPC ABI. Address several problems and

This is a general clean up of the PowerPC ABI.  Address several problems and
bugs including making sure that the TOS links back to the previous frame,
that the maximum call frame size is not included twice when using frame
pointers, no longer growing the frame on calls, double storing of SP and
a cleaner/faster dynamic alloca.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31792 91177308-0d34-0410-b5e6-96231b3b80d8