Rename argument iterators arg_* instead of a*
Remove global variable iterators global_* instead of g*.
Keep the old names for temporary compatibility.
Patch contributed by Gabor Greif!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20591 91177308-0d34-0410-b5e6-96231b3b80d8