[patch] add -Derror global option

[Alexander Belchenko]

Martin Pool пишет:
> This patch
> 
>  * Accepts -Danything as a global option, and stores them into a set of 
>    debugging flags.  (The specific values are not validated, for code
>    simplicity and so that they can be examined by plugins without 
>    needing to get into registration etc; anyhow this is intended for 
>    people who know what they're doing.)
> 
>  * With -Derror a traceback is printed on all errors, even if bzr
>    thinks it's not an internal error.  This is useful because we're 
>    sometimes wrong.

+1.

--
Alexander