Add configure check to verify that boost was built with ICU support
Add an option to skip all of the slow configure checks

Cuts the total runtime of the configure script from 19 seconds to 5
seconds for me.
Simplify icon handling

Eliminate the pointless runtime command name -> icon map and just make
commands responsible for their icons. Don't bother predecoding and
caching icons since it wastes some RAM (~10 MB) and decoding icons takes
a trivial amount of time.

Fix a few places where icons were being set for the wrong command names.
Simplify HelpButton a little

Switch to flat_map for trivially less memory usage and just use a global
map rather than a heap-allocated map since it's not
(de)initialization-order sensitive.
Add 48x48 and 64x64 icons
Use retina icons for the main toolbar if first opened on a retina display
Dynamically switch to the retina toolbar icons as appropriate
Retinafy the video display
Update Indonesian translation