Markesteijn demosaic: floats, OpenMP, & misc fixes

- use floats instead of 16-bit integers
- use OpenMP
- give up interpolation on failed malloc
- use dt's CLAMPS

Note uses OpenMP in outer loop of tile processing rather than many
nested loops. This use NUM_CPUS times more memory, but tiles are small
so this should be OK. Also use OpenMP for cielab_init (though that is
temporary code) and for expanding raw mosaic into rgb buffer.

It's possible there's a race in demosaicing on tile overlaps which would
produce noise at tile edges, but haven't observed this.
use Yuv rather than Lab in Markesteijn demosaic

Thanks to advice from Pascal de Bruijn that this will be nearly
equivalent with much less code, as the colorspace conversion is only
for determining homogenity of image across luminance and chroma.

- try ITU-R BT.2020 YPbPr conversion instead of ITU-R BT.601 as seems
  to do slightly better on specular highlights plus it's so hip and
  cutting edge
- remove spurious luminance added in when doing chroma differential,
  which was a mystery residue of CIELab
- don't need anything from common/colorspaces.h any more
1:1 view demosaicer fixups

This fixes #9388, which applies to all sensors -- make 1:1 view use
chosen demosaicer in mid-quality config.

Update demosaic plugins/darkroom/demosaic/quality conf to mention VNG
in longdescription as x-trans' PPG equivalent. This leaves the config
choice inaccurate for x-trans, but at least doesn't break exsiting
configs. (If change this message to "at most PPG/VNG (reasonable)" then
demosaic will still do the right thing with exiting configs, but the
preferences screen will show a blank entry for this choice
until the user next changes it.)
inpaint highlight reconstruction for x-trans
rawspeed for fuji x-series cameras

- update dngmeta.sh to read 6x6 CFA -- this code could also work for
  2x2 CFAs, though currently each has its own path
- patch rawspeed to handle 14 bpp RAF files -- this may not work in
  all cases, needs more testing
- pre-rotate matrix when load image
- add x-series cameras support in cameras.xml (when in doubt use crops
  as reported in raw file rather than from observation)

White/black levels and crop may differ from libraw version.
document different behavior for x-trans sensors
cleaner edges for Markesteijn demosaic

Make a mirrored/interpolated extra border to give algorithm room to
work. Thank you to Lars Kotthoff for the idea! This version uses more
memory and is slightly slower, but worth it to help the top tier
algorithm do a good job on edges with a lot of detail.