fix hint and gl2 build. NOTE: this does not change that GL2 segfaults right away. that is an issue that dates back at least 50 commits, but most likely even back to the webgl merge. I guess nobody actually tried to run hedgewars in GL2 since back then :P

foreach(dir "Fonts" "Forts" "Graphics" "Locale" "Maps" "Music" "Sounds" "Themes" "Missions" "Names" "misc" "Scripts")
    add_subdirectory(${dir})
endforeach(dir)

if(${GL2})
    add_subdirectory(Shaders)
endif(${GL2})