generator scripts parses new types

[machinaut]

Not quite done for now, but it unlocks a bunch of new mujoco_py.functions

How this is used right now (gross):

import mujoco_py
from ctypes import c_int, addressof

return_value = c_int(0)

# use this in place of `int*` arguments that are used as return values
mujoco_py.functions.mj_aray(addressof(return_value))

# return_value has now been updated (new value) by C function

The better solution is to figure out which int* arguments (all of them?) are used as return values, and have them appended to the return value tuple. Don't have the time for this now, but writing it down for the future.

[machinaut]

cc @bowenbaker

[machinaut]

reviewed by @bowenbaker