Reviewed by oliver
        
        <rdar://problem/5156401> 
        Crash when dragging text into a link inside a table cell

        Test for the crash:
        * editing/pasteboard/5156401-1-expected.checksum: Added.
        * editing/pasteboard/5156401-1-expected.png: Added.
        * editing/pasteboard/5156401-1-expected.txt: Added.
        * editing/pasteboard/5156401-1.html: Added.
        
        Test inserting at the end of a link where we would previously
        insert in the wrong paragraph:
        * editing/inserting/5156401-2-expected.checksum: Added.
        * editing/inserting/5156401-2-expected.png: Added.
        * editing/inserting/5156401-2-expected.txt: Added.
        * editing/inserting/5156401-2.html: Added.

WebCore:

        Reviewed by oliver
        
        <rdar://problem/5156401> 
        Crash when dragging text into a link inside a table cell

        * editing/CompositeEditCommand.cpp:
        (WebCore::CompositeEditCommand::positionAvoidingSpecialElementBoundary):
        Don't avoid the anchor if doing so would skip over a line break, that
        would put content in the wrong paragraph, which can throw ReplaceSelectionCommand,
        which relies on moveParagraphs into infinite recursion.
        Renamed the input position.
        Don't need to re-fetch the enclosing anchor when preparing to push it down,
        since it hasn't changed since the top of the function.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@21078 268f45cc-cd09-0410-ab3c-d52691b4dbfc