Fix bug 2744:

Fix bug 2744:

* buffer.[Ch] (changeRefsIfUnique): extend to handle bibitems
        as well (the function takes a InsetCode argument now);
        clean up by using InsetIterator.

* InsetMathHull.C (doDispatch): changeRefsIfUnique needs a
        InsetCode argument now (bug 2744).

* insetlabel (doDispatch): changeRefsIfUnique needs a
        InsetCode argument now.

* insetbibitem (doDispatch): use changeRefsIfUnique
        (actual fix for bug 2744).

* insetcommand.[Ch]:
* insetcite.[Ch]: implement replaceContents, which is
        used by changeRefsIfUnique.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15289 a592a061-630c-0410-9148-cb99ea01b6c8