Reviewed by Alexey Proskuryakov.

        https://bugs.webkit.org/show_bug.cgi?id=24342
        Cannot insert a Thai character after a Thai prepend character when using ICU 4.0

        This change creates a new break iterator "cursorMovementIterator" for
        moving cursors and use it when moving an input cursor.
        In "TextBreakIteratorICU.cpp", this break iterator uses custom ruleset
        based on the one of ICU 3.8.
        On the other hand, in "TextBreakIteratorQt.cpp", this break iterator
        just calls the characterBreakIterator() function.

        Test: editing/inserting/insert-thai-characters-001.html

        * platform/text/TextBreakIterator.h: Added a new function cursorMovementIterator().
        * platform/text/TextBreakIteratorICU.cpp: Implemented the cursorMovementIterator() function for ICU.
        (WebCore::setUpIteratorWithRules): Ditto.
        (WebCore::cursorMovementIterator): Ditto.
        * platform/text/qt/TextBreakIteratorQt.cpp: Implemented the cursorMovementIterator() function for Qt.
        (WebCore::cursorMovementIterator): Ditto.
        * rendering/RenderText.cpp: Call the cursorMovementIterator() function when moving an input cursor.
        (WebCore::RenderText::previousOffset): Ditto.
        (WebCore::RenderText::nextOffset): Ditto.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@41477 268f45cc-cd09-0410-ab3c-d52691b4dbfc