T_MovePlane()'s code block at the end makes some exceptions to supposedly handle MT_SPINFIRE, MT_SPIKE and MT_GOOP's height properly, however this exceptional handling has proven to be useless at most, and faulty in some cases. While glitch-rocketing spikes up into the air sounds hilarious, I consider the behavior to be undesirable. This merge request removes the faulty code as well as the related line_t.tagline pointer as it served no other purpose.
