lavfi: math typo in interlace filter

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  lavfi: math typo in interlace filter

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avutil/frame: Try to align width to achive linesize[0] alignment

This results in more alignment for pixel formats that have "odd" pixel
sizes like RGB24. It makes access through SIMD easier

Works around Issue described in Ticket1031

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>