Smudge 2nd mode = hard ( by pressing [alt] ).

Useful for painting & photo-retouches.
Smudging while pressing [alt] produces a hard (non smoothed) pixel
displacement. Normal smudge can be combined to smooth the result.
Will be improved to get a complete non-pixel-destructive liquify.
Merge pull request #196 from eVoLuTiVeMEDIA/master

Smudge 2nd mode = hard ( by pressing [alt] ).