Remove dependency on libexpect which had a segfault bug on Arch Linux.
- Replace exp_spawnl() with forkpty() for PTY creation
- Replace exp_expectl() with custom POSIX regex matching
- Update configure.ac to check for forkpty() instead of libexpect
- Update Makefile.am to link with libutil instead of libexpect/libtcl
- Remove expect/tcl packages from all Dockerfiles
- Add Valgrind suppressions for stabber/pthread false positives
* Also pass `$*` to `configure` when invoking `ci-build.sh`, so one can
e.g. run `./ci-build.sh --without-xscreensaver`
Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>
