preparing for a 4.6.4

[Dirk Hohndel]

I know, we've spent all this time on Subsurface-mobile and the bugs there
still aren't fully understood (let alone fixed). But I can't forget about
our main app again - and we really need to get an update out to our users
with the fixed libdivecomputer.

I have two options. I can do a quick new build that uses the new
libdivecomputer and the Subsurface that we used for 4.6.3. Or I can use
the current master and stabilize this.

The advantage of the first option is that we had really really complete
translations for that. The advantage of the second option is that we'd get
the other new things out to our users, including all the fixes to the
planner, the manual entry of depth and duration, etc.

I'm kinda leaning towards the second option but that means we need to
spend a week or two, focused on testing the latest master and finishing
the translations, again. If people have strong feelings one way or
another, please speak up.

I'll do new "daily" builds next and also make sure that all the source
strings are pushed to Transifex, just in case.

Thanks

/D