rice: Fix preprocessor ifdefs.

This code would have failed if it were compiled for OpenGL and the
DEBUGGER symbol were defined.  This fixes the conditional logic.  It
also puts the OPENGL_CHECK_ERRORS back into the gles2 codepath, which
was removed in commit
https://github.com/mupen64plus-ae/mupen64plus-ae/commit/33d250b926141dfd1de72d19b61c8e1b3d7ffda8
rice: Use config file to disable mipmapping rather than hard code.
rice: Narrow the scope of gl/gles2 ifdefs.

It was unclear what the value of several of the boolean options were.
This makes it clearer, and reverts them to what they were before commit
https://github.com/mupen64plus-ae/mupen64plus-ae/commit/33d250b926141dfd1de72d19b61c8e1b3d7ffda8
rice: Remove unneeded macro in osal_opengl.
rice: Revert BOOL-->bool.

See
https://github.com/mupen64plus-ae/mupen64plus-ae/commit/33d250b926141dfd1de72d19b61c8e1b3d7ffda8
rice: Various whitespace & comment touchups.