This mega patch converts us from using Function::a{iterator|begin|end} to

This mega patch converts us from using Function::a{iterator|begin|end} to
using Function::arg_{iterator|begin|end}.  Likewise Module::g* -> Module::global_*.

This patch is contributed by Gabor Greif, thanks!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20597 91177308-0d34-0410-b5e6-96231b3b80d8