Add libclang support for namespace aliases (visitation + USRs) along
with a new cursor kind for a reference to a namespace. 

There's still some oddities in the source location information for
NamespaceAliasDecl that I'll address with a separate commit, so the
source locations displayed in the load-namespaces.cpp test will
change.

llvm-svn: 112676
7 files changed
tree: 4cc7ea5e8e28aa730b5b46dbf8b73593e39684f7
  1. clang/
  2. compiler-rt/
  3. libcxx/
  4. lldb/
  5. llvm/