main.c, pgm.c, pgm.h: Add the -x option to pass extended parameters to

the programmer backend.

jtagmkII.c: Implement the extended parameter jtagchain=
to support JTAG daisy-chains.

avrdude.1, doc/avrdude.texi: Document all of the above.


git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@761 81a1dc3b-b13d-400b-aceb-764788c761c2

pgm.c

@@ -125,6 +125,7 @@ PROGRAMMER * pgm_new(void)
   pgm->set_varef      = NULL;
   pgm->set_fosc       = NULL;
   pgm->perform_osccal = NULL;
+  pgm->parseextparams = NULL;
 
   return pgm;
 }