Support for detection of SWIG and MONO during configuration

[Tamas Szekeres]

Daniel,

According to the IRC conversation I've posted this message to review it more
publicly.

The UNIX build would be more uniform if we could make support for detecting
SWIG and MONO at the ./configure phase.
I would suppose to have optional features should be given as a parameter like

./configure --with-swig --with-csharp

by allowing to add the path to the swig and the csharp compiler executables.
I think for swig /usr/local/bin/swig and /usr/bin/swig
for mono
/usr/local/bin/mcs and /usr/bin/mcs should be searched for by deafault

The other languages may have other requirements.

Any other suggestions would be appreciated.

Thanks,

Tamas