Fix several bugs in the new console resizing code:

Fix several bugs in the new console resizing code:

  - Move initialization of terminal sizes out of UX_initialize_tty
    and into a new function, UX_reinitialize_tty, which does not also
    initialize the stdin/stdout channels, and which UX_initialize_tty
    calls.
  - Call UX_reinitialize_tty, not UX_initialize_tty, in the SIGWINCH
    handler, so that it will not reallocate the stdin/stdout channels
    and potentially overflow the channel table.
  - Don't distribute the CONSOLE-RESIZE event in the CONSOLE-RESIZE
    interrupt handler, since its receivers (recipients?) may perform
    arbitrary computation that should not be performed in interrupt
    handlers.  Instead, signal a thread event to the console thread,
    if there is one, that will distribute the CONSOLE-RESIZE event.