Create module _pyhl

If the configure script was not called with -with-python=no the _pyhl module should be compiled together with the rest of the code. If the configure script was called with -with-python=no, then the best thing is to rebuild the whole HL-HDF package (with -with-python=yes) and installation as descriped in Sections 2.2 and 2.4.

NOTE: Python version 1.5.2 is required to compile _pyhl; otherwise there will be unresolved symbols. Also, be aware that the hdf5 library is linked dynamically which requires that the LD_LIBRARY_PATH contains the path to where libhdf5.so has been installed.