[another test commit, just to tickle the selfhost buildbots; I'll back out in a few...

second round of low-level interface squeeze-out:
making all of CallInst's low-level operand accessors
private

If you get compile errors I strongly urge you to
update your code.

I tried to write the necessary clues into the
header where the compiler may point to, but no
guarantees. It works for my GCC.

You have several options to update your code:

- you can use the v2.8 ArgOperand accessors
- you can go via a temporary CallSite
- you can upcast to, say, User and call its
  low-level accessors if your code is definitely
  operand-order agnostic.

If you run into serious problems, please
comment in below thread (and back out this
revision only if absolutely necessary):

<http://groups.google.com/group/llvm-dev/browse_thread/thread/64650cf343b28271>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107580 91177308-0d34-0410-b5e6-96231b3b80d8