math/saga: Update to 7.9.0

Several bug fixes, enhancements and some new features.
PostGIS version >= 3.0.0 raster capabilities supported

Changelog: https://sourceforge.net/p/saga-gis/wiki/Changelog%207.9.0/attachment/changelog_saga_7.9.0.txt

Reported by: portscout
Approved by: arrowd, tcberner (mentors, implicit)