SaVi satellite constellation visualizer savi-dev

This is a kludge; gcc changes suggest headers and includes
need to be reworked.

Increasing buffer size to stop gcc 11 from complaining.

Minor coverage fix to always show 0...n coverage labels when using land/sea mask projection.

Cosmetic change to Telesat script.

Telesat's constellation is now called Lightspeed, so minor tweaks for that.

Fixing a really stupid bug that prevented display
of the (weakly drawn) sinusoidal map.

Maps need to be redrawn, but that's a different problem.

Simpler way of doing the same window-exists tests.

Always need to check a window exists before
issuing a window command -- in this case, this
was triggered in geomview -run ./savi
by selecting 'Use generated coverage map'
then 'Show equatorial plane'.

Code could be cleaned up with a new function.

Adding in first cut at a Viasat LEO application,
based on their May 2020 modification to their
MEO filing.

Tidied up script groupings.