ergm_Cstate_clear: Deallocate the C data structures corresponding to an ergm_state left over from a .Call() run.
Description
This function is exported for use by other packages that use the ErgmState C API. It should be used as a part of an on.exit() call in the function that calls the C routine if the C routine contains R_CheckUserInterrupt() calls, in order to ensure that memory is freed if the routine is interrupted.