Correct cell alignment computation for too small column sizes.

Actually the column size might not even be too small but the size returned by
renderers GetSize() could be too large -- as is the case for spin renderer
currently. And trusting it results in drawing outside of the cell boundary
even when there is enough space inside it, so don't do this and fall back to
left alignment if there is not enough space.

This fixes display of the year column in the dataview sample broken by the
recent changes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62418 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775