Add new 51 thai translation (backport from master).
Fix 2 fuzzy translations in ja.po for darktable-1.2.1.
Merge pull request #238 from tawtao/th-trans-1.2.x

Add new 51 thai translation (backport from master).
cmake: build with libpng 1.5 (from OpenBSD ports)
(cherry picked from commit 97e7ab882ec278e18797b4992e9664faef8f8927)
(cherry picked from commit 2912f8a31820791c5fd07425f4533e685a312e82)
pthreads: disable the default PTHREAD_MUTEX_STRICT_NP behaviour for OpenBSD
(cherry picked from commit 46be9a13a0bb54aeb28f01fb0d718247aba773d1)
(cherry picked from commit be62db8931eadc49133803977dee0372b4f55009)
New danish translation by Thomas Pryds, ported from master.
update RELEASE_NOTES
100% Danish translation. Thanks Thomas Pryd!
updated translation pt_PT - string freeze darktable 1.2.1 release

two new lines added and translated - now 1566 lines.
a few spelling error fixed.
a few lines that were marked as translated but still in english were translated.
[l10n] Update German translation