USE_CLANG_CPP: Link against all Clang libraries

The default libclang.so build is not sufficient because the extended
functionality for querying MangledName and VTableIndex requires clangAST
in the shared library.

Also adds Make.user support.
3.3 API update: use 'const Decl'.
wrapclang.cpp: remove getCXXClassParents

This functionality is available in stock libclang by querying
CXXBaseSpecifier cursors.
Use new cindex.parse() in README

This may report a "fatal error" if system headers cannot be found,
but the translation unit is usually valid. If it is really a problem,
use the ClangArgs keyword arg to pass in include path(s).