Explicitely track if any arguments or return values were removed in

Explicitely track if any arguments or return values were removed in
DeadArgumentElimination and assert that the function type does not change if
nothing was changed. This should catch subtle changes in function type that are
not intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52536 91177308-0d34-0410-b5e6-96231b3b80d8