Fix MSVC build

The demangler added in r193708 from cxa_demangle.cpp uses language features which are not supported by the latest visual studio. In order to preserve the msvc build, this patch restores the previous (non)functionality in windows under msvc by disabling the demangler. 

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@195254 91177308-0d34-0410-b5e6-96231b3b80d8