- sys.c: Added TODO for fixing bug in how leap years are calculated
- Updated g2w and rat to return EXIT_SUCCESS and EXIT_FAILURE instead of 0 or 1
- Updated main function in g2w to explicitly return EXIT_SUCCESS at the end
  of the function; this allows programs calling g2w to more reliably determine
  whether g2w failed or succeeded.
- Updated makefiles for g2w and rat to use -g (debug symbols) CFLAGS instead
  of -O (optimization); this makes it far easier to understand where crashes
  are occurring (e.g. line numbers are included in console crash reports, and
  the source exactly corresponds to the binary, which is not always the case
  when optimizations are turned on).