cext: make parsers.c PY_SSIZE_T_CLEAN
This is needed to avoid a deprecation warning in Python 3.8. I believe
the conversion of int to Py_ssize_t is harmless in the changed
locations. But this being C code, it should be audited with care.
Differential Revision: https://phab.mercurial-scm.org/D6197
#require serve
$ hg clone http://localhost:$HGPORT/ copy
abort: * (glob)
[255]
$ test -d copy
[1]
$ "$PYTHON" "$TESTDIR/dumbhttp.py" -p $HGPORT --pid dumb.pid
$ cat dumb.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/foo copy2
abort: HTTP Error 404: * (glob)
[255]
$ killdaemons.py