Make FindBrightestAstrobj capable of returning multiple Astrobjs

There could be multiple stars that illuminate planets in a binary
solar system.  We need a way to obtain a list of brightest Astrobjs
instead of just one.  FindBrightestAstrobj can do this by passing
more than 1 to resultCount.
Make DrawTextureSphere work with multiple lights

Now you can see a planet in a multi-star solar system lit with
multiple lights.
Make DrawTextureSpheroid capable of having multiple lights

We share some codes between DrawTextureSphere and DrawTextureSpheroid.

The texture rotation calculation seems wrong in DrawTextureSphere.
Random planets become oblate if they spin fast enough

The randomized parameters distribute around Saturn's characteristics,
so we could see planets as flat as Saturn.