Add "make test" target to run pytest

This will create a virtualenv if required.

There is a bit of churn here reverting to autoconf 2.59 in generated
config.h.in and configure

test/Makefile.in

@@ -0,0 +1,19 @@
+srcdir=@srcdir@
+
+all: test
+
+test: venv/bin/pytest fakekey
+	./venv/bin/pytest --hostkey=fakekey --dbclient=../dbclient --dropbear=../dropbear $(srcdir)
+
+one: venv/bin/pytest fakekey
+	./venv/bin/pytest --hostkey=fakekey --dbclient=../dbclient --dropbear=../dropbear $(srcdir) -k exit
+
+fakekey:
+	../dropbearkey -t ecdsa -f $@
+
+venv/bin/pytest: $(srcdir)/requirements.txt
+	python3 -m venv init venv
+	./venv/bin/pip install --upgrade pip
+	./venv/bin/pip install -r $(srcdir)/requirements.txt
+
+.PHONY: test