vchoi_fork

[svn-r2834] 
Purpose:
    Bugfix
Description:
    The stream_test program reported an error under Linux SMP
    for testing the Stream VFD although everything seemed to be fine.
Solution:
    The sender and receiver process which are forked by main()
    called return(retcode) at exit which implies closing open file descriptors.
    Since these are shared this caused a SEGFAULT in either the sender
    or the receiver when exiting.
    Replacing return() by _exit() is the right way to terminate the forked
    processes in this case.
Platforms tested:
    Linux SMP (eirene)