[Python] Allow attribute references to gdb.Value objects

[Paul_Koning@Dell.com]

> IMO, the robustness choice outweighs this consideration.  While a lot of these scripts are for a single-purpose session, I'm finding that we check them in somewhere and adapt them to future bugs.  I'm sure they'll break in all sorts of interesting ways; I'd rather not add one that we *know* will end in breakage.

Ok, I guess I'll drop the idea, and rewrite my own scripts accordingly.

	paul