bind makes a copy of the arguments by default. This is secure if the

bind makes a copy of the arguments by default. This is secure if the
bound object survives the existance of the arguments, but it also breaks
"change by non-const reference"  parameter passing, like in
Alert::askForString. Here the arguments exists the whole bound function
call so we could pass by refernce.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@35789 a592a061-630c-0410-9148-cb99ea01b6c8