- Change Function's so that their argument list is populated when they are

  - Change Function's so that their argument list is populated when they are
    constructed.  Before, external functions would have an empty argument list,
    now a Function ALWAYS has a populated argument list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4149 91177308-0d34-0410-b5e6-96231b3b80d8