bug#1080: 23.0.60; completing-read-multiple is wrong with mouse-2 in *Completions*

[Drew Adams]

emacs -Q
 
Evaluate this:
(completing-read-multiple "Choose: " '("Lllll" Dddddd "Rrrrrr"))
 
Type: `Lll TAB , Ddd TAB ,'
and then choose `Rrrrrr' with `mouse-2' in *Completions*.
 
The result returned is ("Rrrrrr"), not ("Lllll" Dddddd "Rrrrrr") as it
presumably should be.

It seems like `completing-read-multiple' should use a special
keymap for *Completions*, just like it does with
`crm-local-completion-map' and `crm-local-must-match-map'
for the minibuffer, and in that new keymap, `mouse-2' should
DTRT. IOW, treat `mouse-2' similarly to how TAB is treated.
 

In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
 of 2008-10-03 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/g/include
-fno-crossjumping'