Forward port of my recent changes in the 2.8 branch:

Forward port of my recent changes in the 2.8 branch:

 * Force use of floating point math in wxGCDC::DoDrawEllipticArc.

 * Check for 0.5 offset in wxGCDC::DoDrawRoundedRectangle and
   DoDrawEllipse.  Set wxGDIPlusContext to use the offset.

 * Avoid crash in wxStdDialogButtonSizer::Realize if there is no
   negative button.

 * Provide implementations for wxCairoPathData::AddPath,
   wxCairoContext::Clip, wxCairoContext::DrawBitmap,
   wxCairoContext::DrawIcon, and wxCairoContext::GetTextExtent.

 * Fix wxCairoContext::DrawText to draw the text using the upper-left
   corner for the x,y position, not the baseline.

 * Fix wxMacCoreGraphicsRenderer::CreateContext to be able to use a
   wxMemoryDC as the target.

 * Map wxTELETYPE font family on wxMac to a monospace font.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45077 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775