Add Color.ToHexString() method
Fix FormattedText markup parsing to handle attribute values with spaces

e.g. <span font="Lucida Grande">
[Gtk] Fix FastPangoAttrList.AddFontAttribute

There was an exception due to trying to pass the C# wrapper class to the
P/Invoke instead of the native handle.
[Xwt.Wpf] Add ComboBox support to PlaceholderTextAdorner

We also have cases where comboboxes need to be adorned with
placeholder text.
[Mac] Refactor PopoverBackend a little to enable better native integration

The iOS designer needs these exposed APIs
Ensure Toolkit.WrapWidget creates the correct backend for the EmbeddedNativeWidget

Previously, the backend was created by Toolkit.CurrentEngine, even when you explicitly
call something like nonCurrentEngine.WrapWidget(foo)
[Mac] Fix case where popover is blank the first time it is shown
[Mac] Respect the default button in AlertDialogBackend
[Drawing] Fix possible infinite loop
Ensure Toolkit.Type is set when initialized with Application.Initialize* APIs
[Mac] Use the correct font for dialog buttons
[Wpf] Fix issues with PopoverBackend

- De-parent the content when the popover is hidden
- Give the popover a semi-transparent background
 (other backends all have backgrounds- use the same color as Gtk here)
Fix memory leak caused by undisposed memorystream.
Merge pull request #385 from mono/fixMemoryLeak

Fix memory leak caused by undisposed memorystream.
Merge remote-tracking branch 'upstream/master'