cmake/wxWidgets: exclude components we don't need

this makes the wxWidgets library smaller

old wx: 17521784 B
new wx:  5551187 B
diff: -68.3%

old package: 82756 kB
new package: 70988 kB
diff: -14.2%

old time: 37m18s
new time: 29m12s
diff: -21.7%
travis: compile embedded wxGTK, because it shouldn't take long anymore