core: On Windows we depend on having io.strreams.byte-array for utf16
support. Include this in the boot image instead of alien.strings.
ui.event-loop: No need to special-case ui.private now that the auto-use
tool suggests private words.
imap: Use uuids instead of random numbers.
io.backend.unix.macosx: Trying to change instances of USE: to require if
the vocab must be loaded but no symbols are directly depended upon.
zeromq: Opaque unit tests that keep failing are bad. Change to something
we can debug.
Revert "io.backend.unix.macosx: Trying to change instances of USE: to require if"

This reverts commit 4bab33bddb08427a1dbe96fb936b1a9c01ec25ca.
tar: Couple of optimizations.
sequences: Add examples for some words.
tar: Fix comment, just trim tail.
tar: cleanup stack effects, minor things.
tar: cleanup stack effects, make read-data-blocks recursive.