Simplify include/library path discovery
Simplify include/library path discovery

Note that this introduces a *minor* incompatibility when invoking
setup.py: The '--madxdir' argument can be given only once. Passing it
multiple times is now considered an error (which one should we take?).

If library and headers reside in different locations, you should use

    python setup.py build_ext -L<library-dirs> -I<include-dirs>

to specify them manually.

pymad/jpymad,pymad/cpymad,pymad/jpymad,pymad/jpymad,pymad/cpymad