Updating to Boost 1.53
Adding the forgotten boost/utility.hpp
Fixing thread segfault issues with new Boost 1.53

The answer was to use boost::move() on the functors, but since there is AFAIK no
move emulation support for Boost.Function, the fix may only work on C++11
compilers. That needs to be looked into.
Wrapping boost threads in scoped_ptr

Boost.Thread deprecated the copy ctor for threads; this is a better approach.
Only joining threads if they are created
Making sure that clang_completer tests included
Destroying clang data last, after threads done

Otherwise this will cause issues if the clang threads are still trying to
access the clang data.