I've placed an edited version of the latest Marlin firmware (v1.1.6) on my Dropbox at https://www.dropbox.com/sh/z0yhh0eoq1d9ia2/AAAq7BmiHCpk7jkbZNh_P6jka?dl=1
I have it working on my RRG that has an IR sensor and auto leveling enabled. If you're using the standard mechanical Z endstop, you'll want to change const bool Z_MIN_ENDSTOP_INVERTING = false to true (line # 511), and you'll also want to comment out #define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN (line # 602) and #define ENABLE_AUTO_BED_LEVELING (line # 880). Also note the acceleration settings; I should have commented out of all the defaults. I can probably make edits that correspond to standard RRGs towards the end of the week.