Added `InitTimer` to `init` flags.  cleanup: _-prefixed some unused variables.
Code cleanup, factored shared draw/erase code into closure.
Code cleanup: Add `use` decls to shorten paths, factored code for readability.
Refactored code to allow for choosing demo based on command line args.
Code cleanup: reindent default demo.
factoring testsprite code into own file.
Checkpoint: ported testsprite.c to Rust and it seems to run.