io__call_system()

[Christopher Rodd SPEIRS]

I was trying to use io__call_system() and noticed its slightly unfriendly
return values.  This is because the low order 8 bits of the return value are
flags showing why the process ended (core-dumped, interrupted etc), and the
high order 8(?) bits are the actual return value of the program.  My
questions are:  
 - Is the 8 bits as flags a standard.  ie can i just shift the return val right
   8 bits to get the actual return value, or will my results depend on the
   system?
 - Do we want to make the behaviour of io__call_system() friendlier?

Chris