job control for the es shell

[Olaf Rogalsky <Olaf.Rogalsky@physik.uni-erlangen.de>]

A feature, which IMHO is badly missing form the es shell, is job control.
That's why I made a hack that implements it. If your are interested,
you can get it form:
http://theorie1.physik.uni-erlangen.de/rogalsky/es/es.html

Some Notes:
1) The patch makes use of the waitpid subroutine. Make sure, that your 
   C-library has the waitpid subroutine.
2) In contrast to the wait3 subroutine waitpid gives no information on
   rusage. Therefore wait3 support is broken. You have to out comment 
   USE_WAIT3 in config.h manually. (It is possible to replace waitpid
   with wait4, which gives rusage information. Unfortunately I don't 
   have wait4.)
3) A small modification to %interactive-loop is necessary. You can
   change initial.es or supply your own %interactive-loop in .esrc.
   Until I finish the development phase and switch to the maintain/
   bugfixing phase I leave the initial.es untouched and put all job
   control scripting into my .esrc. I included my .esrc in the source.
   
I also patched the LIBREADLINE support: 
1) The saved history gets read in if you set $history. But this is
   a hack and needs to be rewritten.
2) I fixed a memory leak: LIBREADLINE expects the input line buffers to
   be freed by the application.

P.S.: Can anybody explain to me, what the Ref, RefPop, RefReturn etc
      macros are for?
-- 
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I Dipl. Phys. Olaf Rogalsky                 Institut f. Theo. Physik I I
I Tel.: 09131 8528440                       Univ. Erlangen-Nuernberg   I
I Fax.: 09131 8528444                       Staudtstrasse 7 B3         I
I rogalsky@theorie1.physik.uni-erlangen.de  D-91058 Erlangen           I
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