vchoi_fork

[svn-r9786] Purpose:
bug fix and document.

Description:
Unix and probably other systems too, has a small exit value range
such as 1 byte.  So, exit(256) may end up the same as exit(1).
Added caution message to the exit wrappers and changed test programs
to exit(1) when errors detected.

Platforms tested:
tested in copper.  verified here that exit(256) was treated just like
exit(0).