Adjust mklic.pl script

* Fix mixup of CELT and Speex licenses in about dialog.
* Add filter.svg icon license information
Refac mklic.pl. Generate new licenses.h file.

* Adjust the mklic.pl so it generates and uses the newly introduced ThirdPartyLicense struct
* Misc improvements (newline cleanups, varnaming)
* Generate new licenses.h file via mklic.pl