[rfa] Add ``Maintenance Commands'' appendix

[Andrew Cagney]

> Er, how do I do the cross reference bit?
> 
> 
> Like this:
> 
>  You can see these breakpoints with the @value{GDBN} maintenance command
>  @samp{maint info breakpoints} (@pxref{Maintenance Commands}).
> 
> (The node name inside @pxref might need to be changed to the actual name 
> of the new node you are writing; I don't remember how did you call it.)


Thanks.

It is called ``Maintenance Commands''.  Would a link direct to the 
relevant ``maint info breakpoints'' section be better or isn't that 
possible?  (Hmm, probably not, I think I made that chapter a single big 
table).

Andrew