ZynAddSubFx: Fixed fltk not finding freetype header files.

In cases where the freetype headers are not in /usr/include, fltk wouldn't find ft2build.h.
Add FindWine module and use it in main CMakeLists.txt

Old CheckLibraryExists implementation didn't work on my system.
A find module should be better and also easier to maintain.
Merge pull request #22 from Lukas-W/stable-0.4

Fix build problems: Find wine and freetype headers
Merge pull request #24 from diizy/stable-0.4

Merge for now and let's fix things later.