Fix msContourGetOption() to be able to parse values where no min/maxscaledenom is specified, e.g. PROCESSING 'CONTOUR_INTERVAL=20' (#4691)
update RFC92 cmake instructions (#4617)

closes #4617
Updated msautotest
Merge pull request #4692 from rouault/fix_msContourGetOption

Fix msContourGetOption() to be able to parse values where no min/maxscal...