Linux Mint 16 + Python 2.7 fix

When installing pylibconfig on Linux Mint 16 using Python 2.7, setup.py grabs libboost_python-py33.so, which is incompatible (should be libboost_python-py27.so). The fix is to lookup libboost_python.so first (which is symlinked to the right .so) and only then try libboost_python*.so.