TextInput: Fix cursor height
TextInput: Fix cursor height

On many platforms, the current cursor looks too tall. The logic used
in this patch is inspired by what we have in QTextLayout::drawCursor().
It still looks too tall on Mac, but so it does in Qt Widgets.

QQuickTextInput::positionToRectangle() has also been updated for consistency.

Change-Id: I69b8ad246238d54db370db639a319a3edba6d78a
Reviewed-by: J-P Nurmi <b84a892f57a298bb5dae653b4e188948a84d5549@digia.com>

matthewvogt/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative