prevent pline() segfault

prevent pline() segfault

The use of debugpline() in tty_curs() got me wondering what would
happen if debugpline() was called while pline() is in progress.  I
don't know how to trigger the bad coordinate situation, so I put an
unconditional debugpline() in the NHW_MESSAGE case of tty_putstr()
and used DEBUGFILES=wintty.c to enable it.  Instant segfault, and
the backtrace was short and not useful so the stack might have been
clobbered.  I didn't spend any time trying to figure where or why
the segfault occurred.

Change pline() so that if it is called while the previous pline()
hasn't finished yet (ie, recursively), use raw_print() and return
early.  The raw_print message isn't very useful--it pops up wherever
the cursor happens to be, just like the cursor position bug that has
been an issue recently--but does get delivered without any segualt
and isn't completely useless if DUMPLOG is enabled and you save or
quit before the message buffer gets recycled.  Message readability
situation could be improved but avoiding the segfault was my goal.

Putting any debugpline() into *_raw_print() would be inadvisable....