Fix crash that occurs if the cursor is in a table cell when the document class

Fix crash that occurs if the cursor is in a table cell when the document class
is changed
	* src/cursor.C: remove unused 'using std::swap'
	* src/BufferView.C: ditto

	* src/CutAndPaste.[Ch]
	(switchBetweenClasses): replace ParagraphList argument with InsetText
	argument. This avoids an unnecessary swap in lyxfunc.C.

	* src/CutAndPaste.C
	(pasteSelectionHelper): Adjust to the changes above
	(pasteSelectionHelper): Use ParagraphList::swap instead of std::swap.
	This fixes the crash.

	* src/lyxfunc.C
	(LyXFunc::dispatch): Adjust to switchBetweenClasses changes

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@13895 a592a061-630c-0410-9148-cb99ea01b6c8