Changes to allow explicit physical register arguments that have been

Changes to allow explicit physical register arguments that have been
preallocated.  While reg-to-reg dependences were already handled, this
change required new code for adding edges to/from call instructions.
This was part of the extensive changes to the way code generation occurs
for function call arguments and return values.
See log for CodeGen/PhyRegAlloc.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6467 91177308-0d34-0410-b5e6-96231b3b80d8