Change references to the Method class to be references to the Function

Change references to the Method class to be references to the Function
class.  The Method class is obsolete (renamed) and all references to it
are being converted over to Function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2144 91177308-0d34-0410-b5e6-96231b3b80d8