LibMaker: add amigaos4 library generation

[kas1e]

Need to add libgen.lua and all those skeleton files for aos4 library generation code.

Also, probably worth to structure items for the generate button in that way: if we compile it for morphos, then by default button morphos, if compiled for os4, then by default os4 button, of for os3, os3 button.

So making that mean 2 parts : a little change mui code, and create lua generation scrpt with all that skeleton's codes.