tr: interpolate the request ending a macro

For example, in:

  .de XX YY
  .YY

In addition to marking the end of the macro XX, the macro YY
should also be interpolated.
in: increase the size of unread characters buffer
tr: read transparent output escape sequence in tr.c
ren: end diversions with a newline instead of using sbuf_putnl()
ren: better diversion output in fill-mode