rtapi/rt-preempt: name the threads so HAL names show up in ps/top

example output: 3 threads created by 'loadrt threads ...':

mah@ubuntu-10:~/emc2-rtos/tests/hm2-idrom$ ps -Leo pid,tid,class,rtprio,stat,comm,wchan |grep 14050
14050 14050 TS       - SLsl rtapi:0         skb_recv_datagram
14050 14057 FF      98 SLsl base:0          hrtimer_nanosleep
14050 14058 FF      97 SLsl medium:0        hrtimer_nanosleep
14050 14059 FF      96 SLsl slow:0          hrtimer_nanosleep
rtapi_app: name the main thread properly in ps/top

whatever the executable's path name, the process name should always
come out as 'rtapi:<instance number>' so a particular RT instance
can be identified as running.
rtapi/rt-preempt: log HAL name at thread startup too
rtapi/rtapi_app: break long lines

This aids review by VT100 users.

Also, remove unused includes - System V IPC is history.
Fix tests/overrun

tests/overrun/test.sh creates a new test directory, then calls
runtests on it.  Commit 05c8f859 breaks this, since the realtime
script is called once from the outside runtests script and again from
the inside one.

Hack this by stopping realtime before the inner runtest run, and
starting it again afterwards.  Yowch!