darktable 1.6.4

this is a point release in the stable series. the sha256 sum is

c5f705e8164c014acf0dac2ffc5b730362068c2864622121ca6fa9f330368d2a darktable-1.6.4.tar.xz
e5bbf00fefcf116aec0e66d1d0cf2e2396cb0b19107402d2ef70d1fa0ab375f6 darktable-1.6.4.dmg

and as always, please don't use the tarballs provided by the snapshot buttons on github.

general improvements:

• major rawspeed update
• facebook exporter update (first authentication usability should be much better now)
• first run opencl benchmark to prevent opencl autoactivation if gpu is obviously slower than cpu
• lensfun cornercase fixes
• some mask cornercase fixes
• zonesystem now updates it's gui when number of zones changes
• spots iop updates
• ui_last/gui_language should work more reliably now
• internal lua updated from 5.2.3 to 5.2.4 (distro's typically use their own version of lua)
• gcc 5 should build now

new camera support:

• canon digital rebel (non european 300d)
• nikon d5500 (experimental)
• olympus e-m5 mark ii (experimental)
• Samsung NX500 (experimental)

white balance presets:

• sony a77 ii
• fujiflim x-e2
• olympus e-m5 mark ii

noise profiles:

• canon 7d mark ii

updated translations:

• german
• french
• russian
• danish
• catalan
• japanese
• dutch