Fix mangling of array parameters for functions in the Microsoft C++ Mangler.

Fix mangling of array parameters for functions in the Microsoft C++ Mangler.
Only actual functions get mangled correctly; I don't know how to fix it for
function pointers yet. Thanks to John McCall for the hint.

Also, mangle anonymous tag types. I don't have a suitable testcase yet; I have
a feeling that that's going to need support for static locals, and I haven't
figured out exactly how MSVC's scheme for mangling those works.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107561 91177308-0d34-0410-b5e6-96231b3b80d8