Handle cell alignment in the renderer itself in generic wxDVC.

Handle cell alignment in the renderer itself in generic wxDVC.

Instead of using wxDataViewRenderer::GetSize() and rendering the cell into the
appropriate part of the rectangle, pass the full rectangle and the alignment
of the cell contents in it to the renderer itself.

This fixes the bug with bold text being truncated in the "attributes" column
of the dataview sample and is also generally more flexible as the renderer may
decide itself what to do with the extra space.

It also somewhat reduces the code duplication between CreateItemBitmap() and
OnPaint().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62393 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775