bug#13561: 24.3.50; `dired-do-run-mail' should ask for confirmation first

[Drew Adams]

Here's the problem:  `V' is bound to `dired-do-run-mail'.  And it is too
easy to accidentally hit `V'.  I just hit it instead of `B', for
instance, after marking some files to byte-compile.
 
Instead of asking for confirmation, it went off and tried to do its
thing, ultimately resulting in an error message etc.
 
In general, commands that act on the marked files should require some
user interaction before doing their thing.  Often it is enough that they
prompt for some info, for the user to at least be able to see whether
s?he has got the right command.  If they do not prompt for any info,
then they should, in general, ask for confirmation.
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2013-01-25 on ODIEONE
Bzr revision: 111604 eliz@gnu.org-20130125143821-1ykj7ia1qjojjjnp
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -IC:/Devel/emacs/build/include --ldflags -LC:/Devel/emacs/build/lib'