State before: in chrono:userlib, there were second-resolution
@da-to-unix and unix-to-@da functions. In en/dejs:format, there were
millisecond-resolution @da-to-unix and unix-to-@da functions. The
@da-to-unix path in time:enjs confusingly rounded to the nearest
millisecond, meaning millisecond n was a label for [n-0.5, n+0.5) rather
than [n, n+1).
This adds a millisecond-resolution @da-to-unix and unix-to-@da to
chrono:userlib, and a second-resolution conversion to en/dejs:format.
It makes use of the chrono:userlib functions in en/dejs, and doesn't do
any rounding.
Backwards-incompatible changes:
- made unt:chrono:userlib take a @da rather than @.
Unflops the spur in +en-beam, +de-beam, and everything that calls either
of those, or works with the consequences of their output.
This includes clay's interface for mounting and unmounting, which now
no longer expects the arguments to contain an old-style spur.
