Compiles a list of adjacent elements for the specified element.
(tpm_elemadj tpm_id elem_id adj_type)
Returns a list of element IDs or nil.
| tpm_id | Topology ID (real) |
| elem_id | Element ID, received from tpm_elemid |
| adj_type | Type of adjacent elements (int). Values: 1 Node 2 Pink 3 Polygon |