[LLDB] Use the llvm microsoft demangler instead of the windows dbghelp api. NFC.
[LLDB] Use the llvm microsoft demangler instead of the windows dbghelp api. NFC.

If there's any testcases that only do demangling (I didn't find any),
they could be made available for all platforms now.

Differential Revision: https://reviews.llvm.org/D68134

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@373144 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb