FCxtrans() returns int to conform with FC()
demosaic: speed up xtrans_markesteijn_interpolate()

Ideas, suggestions, and code with thanks to Ingo Weyrich:

- tune tile size
- don't add 6 to CFA offsets unless they're actually negative
- homogeneity buffers can reuse existing memory
- eliminate conditional when building homogeneity maps (gives 15%
  speed increase)
- pre-build 5x5 sums of homogeneity maps (another 15% speed increase)

Conflicts:
	src/iop/demosaic.c
demosaic: more Markesteijn clean-up/optimization

- as per Ingo Weyrich, set TS to 88 to try to keep data in a
  reasonable sized L2 cache
- cleanup buffer sizes/offsetes a bit more
- optimization from Ingo Weyrich, make yuv indexed by channel first
- use sizeof(uint8_t) in memset, even if it is 1
- for a few uint8_t-derived local variable, type them as uint8_t
tile min/max green calc, tile output

Use Ingo Weyrich's idea of a per-tile min/max green buffer, rather
than storing min/max in g1/g3 of intermediate image array. This allows
the intermediate array to be only 3 rather than 4 channels, reducing
memory consumption. This means no need to access the intermediate
image buffer during the rest of the tile processing, as the rgb[0]
buffer has the same data. Furthermore, write processed data directly
to the out[] buffer when have finished each tile, which saves a final
copy loop and gives an approx. 20% speedup.

allhex is now only useful in terms of tilesize as it only finds offsets
in rgb tile, not in the original image.
demosaic: fcol() offset note

row & col params can be -1 or -2; note this in comments as the
rationale for +6 then modulo 6

Conflicts:
	src/iop/demosaic.c

Conflicts:
	src/iop/demosaic.c
eliminate Markesteijn demosaic intermediary buffer

Additionally more speed-ups and better constants thanks to Ingo Weyrich.

Conflicts:
	src/iop/demosaic.c
collect: fix crash in case of non-valid utf8 database entries

g_markup_escape_text() does not tolerate invalid utf8 strings.
we need to to fix those upfront.
simplify float X-Trans downscale/demosaic

get rid of code copied from Bayer version which isn't necessary as are
not aligning calculations to the sensor CFA
update pt_BR master
Merge pull request #635 from guitorri/master

update pt_BR master
Try to add sane defaults to an empty XDG_DATA_DIRS
Merge pull request #632 from upegelow/collect_utf8_fix

collect: fix crash in case of non-valid utf8 database entries
Fix help message for picasa module

What the user needs to copy is the code given in the page, not the URL
Updated Dutch translation
Merge pull request #638 from MRIG/master

Updated Dutch translation
Merge pull request #631 from dtorop/markesteijn-improvements

demosaic: x-trans Markesteijn improvements
Make dt-cli work without X

Just ignore the warnings/errors for now ...