Properly remove the sdl-* submodules.

Oops.
Tab harder (|amethyst).

Oops.
A couple of Android build improvements.

Pass Makefile flags to ndk-build; import CFLAGS/CXXFLAGS from the main
Makefile.
We don't actually have a CXXFLAGS_L, so don't try to use it.

Oops.
Properly pass flags to ndk-build.
More Android-related Makefile cleanup.

Perhaps we do need an ALL_CXXFLAGS or similar.
Specify (semi-)necessary Android build flags by default.
Use arm mode for Android arm builds and not thumb mode.

...since the latter is now failing to build for some reason.
Android: handle fonts and save dir properly again.