video-orc: fix v_2tap_u16
video-scaler: fix phases in interlaced mode
video-scaler: fix taps in interlaced mode
video-scaler: fix temp line allocation

We need to allocate the templine with the amount of pixels we are going
to handle, which we only know for the vertical resampler when we are
asked to resample.
video-converter: rework the converter to allow more optimizations

Rework the converter, keep track of the conversion steps by chaining the
cache objects together. We can then walk the chain and decide the
optimal allocation pattern.
Remove the free function, we're not going to need this anytime soon.
Keep track of what output line we're constructing so that we can let the
allocator return a line directly into the target image when possible.
Directly read from the source pixels when possible.
video-converter: pass output line correctly
video-scaler: avoid memcpy when not needed
video-converter: keep separate lines with border

Make separate with a border around them so that we can avoid a memcpy.
test : fix leaks in adder unit test

https://bugzilla.gnome.org/show_bug.cgi?id=739640
tests: dist header file needed for ABI checks on powerpc32

Fixes 'make check' on debian powerpc32 buildbot:
libs/libsabi.c:95:26: fatal error: struct_ppc32.h: No such file or directory
video-chroma: do h subsampling after v subsampling

We only need to do the horizontal subsampling on 1 line if we do it
after vertical subsampling and we also avoid doing vertical subsampling
on unused pixels.
video-format: fix range extension of UYVP

We need to shift the top 6 bits to the lower 6 bits
video-format: fix pack of 4:2:0 formats

When packing 4:2:0 formats, we need to take the chroma from the even
lines, for the odd lines we only take luminance.
video-format: add range extension to BGR_10XE format
video-format: update some docs and add a FIXME(2.0)
tests: get the correct number of video formats

Make a method to get the number of formats (including the last one).
tests: make pack/unpack test

Make a more complete pack/unpack test, check if the image after
pack/unpack has the same color and precision, and has correctly
duplicated subsampled pixels.
video-chroma: optimize chroma subsampling a little

Combine multiplies in 4x filters.
Rename conversion functions to make them nicer in orc.
Add ORC versions for various downsampling algorithms
Add unit test chroma resampler
video: Update disted orc files
video-converter: add more debug