gettimeofday() is subject to be changed on daylight-saving or to ntp-related
(think leap-seconds). even worse, it is subject to be changed BACK in time. this
is hard to fix correctly (see commit 45726d3016 and bug #3560509). it is
irrelevant for timers to know the nano-seconds since the epoch anyways.
a 'BidiString' holds both the logical content and the visual reordered
version of the content of a string. this helps to reduce the number of
calls to reorder the string before drawing it (as introduced in the patch
from Ken Bloom) and to be more consistent in menus and textboxes (drawing
cursors and underlining text).
