Add support for the pan language

Add pan http://en.wikipedia.org/wiki/Pan_(programming_language) as a supported language.
There is a collision with file extension for smarty templates, so make sure that is handled nicely.

I have written test cases but can't check them at the moment due to the following error:
<pre>
run_tests: test/unit/detector_test.h:119: test_detector_detect_polyglot: Assertion `lang' failed.
Aborted
</pre>