changes to gdb-ui.el and gud.el

[Nick Roberts]

I have now changed gdb-ui.el so that it uses the speedbar to watch
expressions. In the parlance of the GDB developers, this feature uses variable
objects which are part of GDB/MI (MI = machine interface). This is necessary
as they are proposing to make annotations, the interface gdb-ui.el has been
using, obsolete. It is cleaner and does not involve parsing output that is
really meant to for the user. It certainly makes it easier to control the
display of complex structures and their values.

Update of the speedbar for arrays and structures can be pretty slow at the
moment but does demonstrate the concept. I am trying to speed things up by
replacing alists with hash tables. Any help in this respect will be
appreciated.

To use this feature YOU NEED TO HAVE GDB VERSION 6.0 which is on the point of
being released and will be available at http://ftp.gnu.org/gnu/gdb/ or one of 
the
mirrors. Everything apart watching expressions should work with earlier versions
of GDB.

I have made changes to gud.el but this should not affect M-x gdb.

Any feedback, good or bad is most welcome. (I'm away for 5 days)

Nick