[mcs] Adding unit test for #18511
[mcs] Fix recursive resolving of crefs (#18511)
[xbuild] Add GetAssemblyIdentity task to Microsoft.Common.tasks
Prevent call to OwnerLostFocusHandler for disposed object

bugzilla.xamarin.com bug reference: Bug 19304
ComboBox reverts to original selection when it loses focus.
The LostFocus handler for the internal ComboTextBox class
was being called after it had been disposed.  The dispose
was correctly called when the ComboBoxStyle changed from
it's initial default value to DropDownList.  However, when
the ComboBox control lost focus later on, the LostFocus event handler
was called, which resulted in the Text value for the ComboBox
being overwritten by the value in the disposed object.

Could not see how to write a unit test within the ComboBoxTest.cs
that would simulate losing focus so only providing fix.

Change-Id: I9ca4cc75da5711a7d7c1dd166d5f52d580f44df1
Merge pull request #1008 from lambdalice/master

[xbuild] Add GetAssemblyIdentity task to Microsoft.Common.tasks
Small touchups to the UI, remove some extra space, use a bold, large font for the text
[DbDataReader] Implement GetFieldValue<T> function to make mono working with EntityFramework 6.x
Add a `check` target to mcs/errors/Makefile.
Add .gitignore file in mono/arch/arm64.
Backport some changes from nunit/nunitv2 that hopefully fix some test agent hangs.
Merge pull request #1011 from Fabian-Koenig/master

[DbDataReader] Implement GetFieldValue<T> function to make mono working with EntityFramework 6.x
[linq] Use hashtable lookup instead of linear scan for groupby keys. Fixes #18673
Merge pull request #966 from ermshiperete/bug-xamarin-18511

[mcs] Fix recursive resolving of crefs (#18511)
[mcs] Caching of type argument types should not happen under error conditions. Fixes #18282
Updated HTML reference test output
[mcs] Better fix for 0d11522afeb4f7a21a68937d27153f00c11a43fa to consider full member accesibility
wip
might be working
[runtime] Fix use before null-check crasher. Found by PVS Studio.
Revert "might be working" Stupid me pushed a working branch. Glad it had no swearing.

This reverts commit a9d74622fd1c876249203a6ad208e2757350e6dd.