Fix build problems: Find wine and freetype headers

Fltk in ZynAddSubFx module can't locate freetype headers (specifically ft2build.h) if they are not in /usr/include. Fixed by using output variable of FindFreetype.cmake.

Finding wine didn't work for me and the current (5-year-old) script to locate it looked weird and unusual to me. I replaced it using a find module. I guess this is the more convenient approach.