opendream_compiletimereadonly doesn't work inside proc code

[Toastical]

/turf/Initialize(mapload)
	src.random_var = FALSE

random_var is marked as opendream_compiletimereadonly on turf inside DMStandard/Types/Atoms/Turf.dm. It's caught if in an object definition, but not inside procs.

[ike709]

The issue is due to the fact that the only time opendream_compiletimereadonly gets checked ever is on DMCodeTree.ObjectVarOverrideNode