Split in library and application

[Laserlicht]

Many thanks for developing innoextract.

It would be great to split it in library and application. That we basically have a libinnoextract. I think many other projects can make use of it.

Because not in every case it's possible to call a command line program (e.g. android/ios).

[grepwood]

@dscharrer can you please take a look at this? VCMI, the free software rewrite of Heroes of Might and Magic 3 engine, would like to consume innoextract as a library, so that its launcher may offer extracting game data from offline GoG installers.