[Demangle] Add a few more options to the microsoft demangler

This corresponds to commonly used options to UnDecorateSymbolName
within llvm.

Add them as hidden options in llvm-undname. MS undname.exe takes
numeric flags, corresponding to the UNDNAME_* constants, but instead
of hardcoding in mappings for those numbers, just add textual
options instead, as it the use of them here is primarily intended
for testing.

Differential Revision: https://reviews.llvm.org/D68917

llvm-svn: 374865