Make some text translatable

[huobos]

I found some text are not translatable during Chinese translation. Make them translatable.

[rnorris]

Thanks for these, however I don't think I can directly use this commit.

For instance the calls to vik_waypoint_set_symbol() are to an internal lookup table and then match a specific Garmin GPX symbol text. I think the text is the interface and hence not translatable.

For OSM map types in osm.c - there's probably more translations too add.

Some other cases I may have to consider further where the appropriate place for the '_( )' should go, although mostly it appears correct.

Thus I expect to manually review each change in slow time and probably commit in smaller chunks for a more fine grained control (e.g. the changes that just replace gettext with _).

And then I'll apply your additional Chinese translations that are still relevant (most of them) in one go.

Hopefully this is an agreeable approach.

[rnorris]

I've broken down the commit into various smaller commits and applied to the repo.