BUGFIX: max_user_ip was broken: initialising to -1 meant that the ACL appeared

BUGFIX: max_user_ip was broken: initialising to -1 meant that the ACL appeared
        already configured to the parser, and thus it never configured to a
	valid value. Fixed with a test case to ensure that a normal ACL line
	will parse the -s and the limit values correctly, and a separat test
	that the defaults are as expected.