- Default Gecko Compatibility which is Gecko slice added to Native (for web compat)
- other modes pure native (no gecko slice) and Firefox compatibility (Gecko+Firefox+rv: changed to Firefox compat version)
This removes `general.useragent.compatMode.firefox` and `.gecko` in favor of an int pref.
See also: MoonchildProductions/Pale-Moon#466
- Also clean up leftover dead files that weren't cleaned up by Mozilla's graphite updates
- Also revert BMO 1255731 which was just a cheap solution to not back-port graphite 1.3.7 to ESR38