overlays: fixed stereo offset of subtitle was applied when not in 3d
overlays: apply stereo offset to all overlay types

This fixes issue #14926

Note: dvd/bluray menu's will not align properly if played back in
a stereoscopic mode after this change, but it's an okey trade off
for now.
Merge pull request #4209 from elupus/stereoscopic

Stereoscopic subtitle offsets