It's pretty easy to do it yourself. Go to raw/objects and open body_default.txt and replace the whole [BODY:QUADRUPED] entry with the following:
[BODY:QUADRUPED]
[BP:UB:upper body][UPPERBODY]
[BP:LB:lower body][CON:UB][LOWERBODY]
[BP:HD:head][CON:UB][HEAD]
[BP:RUA:right front upper leg][CON:UB][LIMB][RIGHT]
[BP:LUA:left front upper leg][CON:UB][LIMB][LEFT]
[BP:RLA:right front lower leg][CON:RUA][LIMB][RIGHT]
[BP:LLA:left front lower leg][CON:LRA][LIMB][LEFT]
[BP:RH:right front foot][CON:RLA][STANCE][RIGHT]
[BP:LH:left front foot][CON:LLA][STANCE][LEFT]
[BP:RUL:right rear upper leg][CON:LB][LIMB][RIGHT]
[BP:LUL:left rear upper leg][CON:LB][LIMB][LEFT]
[BP:RLL:right rear lower leg][CON:RUL][LIMB][RIGHT]
[BP:LLL:left rear lower leg][CON:LUL][LIMB][LEFT]
[BP:RF:right rear foot][CON:RLL][STANCE][RIGHT]
[BP:LF:left rear foot][CON:LLL][STANCE][LEFT]
It's functionally identical to the humanoid body with the exception of the [STANCE] tags on the front feet and the name of the entry, and splits the legs into two parts each. Since the names of the body parts are the same (that's RUA and LUA, etc, not the text descriptions), you can use humanoid joints without any further modification to the body_default file. You add the joints to your quadrupeds by running through each of the creature files (creature_[whatever].txt) and changing "QUADRUPED" to "QUADRUPED:HUMANOID_JOINTS". That needs to be in all caps -- as a rule, everything needs to be in caps with the exception of text that the game displays.