Broken "Duke-Tag!" announcement sounds

These can be played back in E4L10's "Duke-Tag!" mode upon obtaining a pair of boots, and also when scoring for a team.

The problem is also relevant for NetDuke32 and Rednukem.

Changing S_PlaySound3D to ignore S_PlaySound's return value, and unconditionally return 0 instead, appeared to fix the problem in all of EDuke32, NetDuke32 and Rednukem; This is a bit closer to the original DOS code, but I'm unsure it's the correct solution. I also tried returning -1 instead.