[GTK] Properly save/restore global alpha
[Mac] Fix Label default background color.

Even if you disable background drawing of an NSTextField, it will retain its default background color or Developer/textBackgroundColor which is solid white. Force the color to transparent when initializing the view so that this default is not propagated.
Add calling convention to DllImports.
Add a new hack to look for monomac in one more location

This is to cope with the restructuring of some of our code
Fix crash when rendering markdown

When rendering a link, don't crash if the uri is not valid.
[WPF] Resize bitmap before drawing if necessary.

When an image is a single bitmap that doesn't have the same intrinsic size as the drawing size, dc.DrawImage makes a very poor job of down/up scaling it.

Thus we handle this manually by using a TransformedBitmap to handle the conversion in a better way when it's needed.
Merge remote-tracking branch 'upstream/master'