Centralize and refine the __unknown_anytype argument rules
and be sure to apply them whether or not the debugger gave
us a method declaration.

rdar://12565338

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176432 91177308-0d34-0410-b5e6-96231b3b80d8
Correction to r176432: the bug actually fixed was <rdar://13025708>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176433 91177308-0d34-0410-b5e6-96231b3b80d8