glide: Synchronize unused files with upstream.
glide: Consolidate frameskipper source files.
glide: Simplify frameskipper implementation a bit.

ticksInitialize() was never being called, hence startTicks was always
zero.  Therefore both can be removed.

Rename ticksGetTicks() -> getCurrentTicks() and make it a private
method rather than static.
glide: Initialize all frameskipper fields in constructor.
glide: Document and rename frameskipper variables for clarity.
glide: Simplify frameskipper conditionals for better readability.

And don't perform computations that aren't needed in manual frameskip.
glide: Change build flag ANDROID_EDITION -> USE_FRAMESKIPPER.

More general and clearer meaning.