Hst hst

Use shared_ptr from Boost instead of from the TR1 standard

When we first used shared_ptr in the HST code, we weren't using Boost yet. shared_ptr is in TR1, which seems to be implemented by most modern C++ compilers, so it made sense to use that implementation, rather than introduce a dependency on Boost.

Now, though, we're using Boost for other things, so it makes sense to just use the shared_ptr implementation from it. This also fixes a bug reported by Moritz Kleine, where we'd get an error when trying to compile src/assertions/refine.cc, since the compiler could somehow see both implementations of shared_ptr, and would get confused which one to use.

As part of this patch, I've also removed all “using namespace” statements from the header files, since I've discovered that this is rude behavior in the C++ world. (We don't want to require the users of the header files to use the namespace, too, after all...) http://github.com/hst/hst/commit...