Consistency patches to Module and Function

Dear llvm-devs,

we discussed a consistency issue with the naming of
iterators in the #llvm IRC channel and I came up
with a patch to Module.h and Function.h.

The patch renames the aiterator family of typedefs
to arg_iterator in Function and correspondingly
giterator and friends to global_iterator.
The accessor functions also change accordingly.

Right now the old spellings are preserved, but
will go away after some time. So this is a heads-up
to do a global replace in your non-LLVM-CVS codes
from the old names to the new ones.

The change is blessed by Chris Lattner and the
others on IRC seem to support it too, I hope it is
not much of a fuss for your projects. If yes, please
give feedback. The patch will be committed by
Chris soon, so you can have a look at it.

Happy coding,