Merge xargs(1) with that of xMach.
Bring in xargs(1) changes to add -L and -I as per the Single Unix Specification
version 3. Proper exit status numbers are implemented, and the manual page has
been updated to reflect reality.
The code has been ANSIfied, and a new file has been added to xargs(1) to do the
substring substitution as SUSv3 requires.
Traditional behaviour should not be affected, use of -J should be deprecated
in favor of the more portable -I (though -J has been left, for now).
Submitted by: me, tjr (the exit status stuff)
Obtained from: xMach