Correct QDeclarativeTextEdit::positionToRectangle().

d->yoff is the content offset when the content is not top aligned.
This means that positionToRectangle() returned incorrect values when
the content was bottom or vertical center aligned. In other words,
it didn't apply the offset but gave coordinates from the beginning of
the content instead of from the beginning of the item.

Change-Id: I044b79434b9a67b0539050e39953d5889a3ed1db
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Ensure TextEdit's text is vertically aligned after resizing its height.

The current code only updates the alignment if the width of the
TextEdit changed, but we must also check if the height has changed.

Task-number: QTBUG-36069

[ChangeLog][QtDeclarative][TextEdit] Fixed TextEdit not vertically
aligning its text after having its height changed.

Change-Id: I428a01111874c70d2151213d2b3c5553e7f21186
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>