Upstream STP's libstp now depends on boost. This commit updates
the configure script to detect this by first trying to link without
boost and if that fails then trying to link libstp with boost.

This also updates the relevant Makefiles so that the klee and kleaver
executables link in STP's boost dependencies if necessary.
Fixed compilation of unittests with upstream STP (Boost dependency).
Merge pull request #99 from delcypher/feature_support_stp_with_boost

Upstream STP's libstp now depends on boost.