math/saga: Update to 9.1.0

Minor release with many improvements, new features and bugfixes.

• Moved tools from VIGRA to OpenCV
• Clipper2 upgrade to v1.2.2
• Pointcloud improvements and new features
• Parallization of topographic correction
• Supervised classification: training samples option added
• Cloud and cloud shadow detection tools added
• Several improvements for the 3D view panel and map
• Add a Python package PySAGA for saga-python-api
• Moved several tools to better places
• ...

Changelog: https://sourceforge.net/p/saga-gis/wiki/Changelog%209.1.0/attachment/changelog_saga_9.1.0.txt

Reported by: portscout, Repology