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 init test
$ cd test
$ cat > .hg/hgrc <<EOF
> [extensions]
> # this is only necessary to check that the mapping from
> # interhg to websub works
> interhg =
>
> [websub]
> issues = s|Issue(\d+)|<a href="http://bts.example.org/issue\1">Issue\1</a>|
>
> [interhg]
> # check that we maintain some interhg backwards compatibility...
> # yes, 'x' is a weird delimiter...
> markbugs = sxbugx<i class="\x">bug</i>x
> EOF
$ touch foo
$ hg add foo
$ hg commit -d '1 0' -m 'Issue123: fixed the bug!'
$ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
log
$ get-with-headers.py localhost:$HGPORT "rev/tip" | grep bts
<div class="description"><a href="http://bts.example.org/issue123">Issue123</a>: fixed the <i class="x">bug</i>!</div>
errors
$ cat errors.log
$ cd ..