Update children positions when parent body is modified

[375gnu]

At least with the build from the pull request, locations on Ceres are fixed with its actual oblateness, but I just found that if I modify an object to increase its oblateness to 0.5, locations are still floating in space:

Originally posted by @SevenSpheres in https://github.com/CelestiaProject/Celestia/issues/1557#issuecomment-1666610049

[375gnu]

@SevenSpheres are you sure that you tested a proper build? That's what I have with the today's master:

[munix9]

works for me too (linux/qt5/master)

[SevenSpheres]

Still looks like my screenshot on the latest build. Tested on Win32, Qt5, and Qt6 frontends.

[ajtribick]

I can reproduce both cases.

• If you edit the oblateness of Mars by editing solarsys.ssc, the location positions work.
• If you set it via a modification rule, e.g. Modify "Mars" "Sol" { Oblateness 0.5 } then the location positions will not be updated and will be floating in space.

[SevenSpheres]

Can confirm, so this is probably a non-issue

[375gnu]

Then we need to recompute children positions on modification.