Support visual cursor movement for BIDI text

Support visual cursor movement for BIDI text

Bidi input can in some contexts be more intuitive if the cursor
works in visual way: pressing left arrow key always make cursor
move one character to the left regardless the language of text,
pressing right arrow key always make cursor move to the right.
It is also the behavior of Mac OS X. Based on the above reason
and requests from Symbian we implemented this support for visual
movement in BIDI text. 3 public properties are added to
QTextDocument, QTextLayout and QLineEdit respectively:

- QTextDocument::defaultCursorMoveStyle can be used to control
  the cursor behavior in all widgets based on QTextDocument,
  like QTextEdit, QPlainTextEdit, etc. When set to QTextCursor::
  Visual, it will enable visual movement for all the cursors in
  the corresponding text edit. Default is QTextCursor::Logical.

- QTextLayout::cursorMoveStyle is used for low-level cursor
  manipulation. When set to Visual, it will enable visual movement
  behavior for all the cursor related methods, including cursorToX,
  xToCursor and drawCursor. Default is Logical.

- QLineEdit::cursorMoveStyle is used to control cursor movement
  behavior in QLineEdit. Default is Logical.:

Task-number: QTBUG-13859
Reviewed-by: Eskil
(cherry picked from commit c480dd641f5d22d1ee72cb27bf39e24c6df65658)