r8671: use much shorter names for the selftest directory and socket wrapper

r8671: use much shorter names for the selftest directory and socket wrapper
code. I'm afraid this is needed by irix 6.4 which silently truncates
names in unix domain sockets in recvfrom() to 16 chars. My apologies
for having to move to such short names :-(
(This used to be commit f9693e313da67e1347a607db5d3ebbf36e02a77a)