Fix warnings and errors in the Android build process

[player-03]

This addresses the (reproducible) issues brought up in #1476, plus some that came up when testing the changes.

[player-03]

Apparently this breaks PiratePig. Something to do with uploading textures, which is odd because none of these changes should have affected much of anything.

I was hoping to get this merged in time for the next release, but now that's off the table. This is apparently not the self-contained change I thought it was, and will require extra testing.

[player-03]

Ok, so it turns out I messed up the tagged pointer workaround. PiratePig works fine when I include it. That said, I still don't plan to merge just yet, in case someone else finds something.