[RFC][python] Add support for commands implemented in Python

[Eli Zaretskii]

> From: Thiago Jung Bauermann <bauerman@br.ibm.com>
> Cc: gdb-patches@sourceware.org
> Date: Thu, 05 Feb 2009 20:40:05 -0200
> 
> gdb/doc/
> 2009-02-05  Tom Tromey  <tromey@redhat.com>
> 
> 	* gdb.texinfo (Python API): Add entry for Commands In Python.
> 	(Commands In Python): New node.

Thanks.  My only comment to the new text is that perhaps the COMMAND_*
constants should have followed the respective GDB command classes more
closely.  For example, COMMAND_RUNNING instead of COMMAND_RUN,
COMMAND_DATA instead of COMMAND_VARS, etc.  But that's a minor
concern, especially if you had a good reason to deviate from the GDB
interactive nomenclature.