pt_sendto_cont need to deal with the possibility of a zero-length buffer.
r=srinivas@netscape.com. Added a test zerolen.c for this bug.
Modified files: ptio.c, pr/tests/Makefile, pr/tests/Makefile.in,
pr/tests/runtests.ksh.
Added file: pr/tests/zerolen.c
wtc%netscape.com