CLR COM Event Handler returns E_INVALIDARG and Array Data is not Updatted when Event Parameter is double pointer to SAFEARRAY. (microsoft#975)

* CLR COM Event Handler returns E_INVALIDARG and Array Data is not Updated when Event Parameter is double pointer to SAFEARRAY.

* Address pr feedback

Author: jeffschwMSFT

Documentation/compatibility/interop-event-handlers-safearray.md

@@ -0,0 +1,28 @@
+## .NET COM successfully marshals ByRef SafeArray parameters on events
+
+### Scope
+Minor
+
+### Version Introduced
+4.8
+
+### Source Analyzer Status
+NotPlanned
+
+### Change Description
+In the .NET Framework 4.7.2 and earlier versions, a ByRef [SafeArray](https://docs.microsoft.com/en-us/windows/desktop/api/oaidl/ns-oaidl-safearray) parameter on a COM event would fail to marshal back to native code.  With this change the [SafeArray](https://docs.microsoft.com/en-us/windows/desktop/api/oaidl/ns-oaidl-safearray) is now marshalled successfully.
+
+- [ x ] Quirked
+- [ ] Build-time break
+
+### Recommended Action
+If properly marshalling ByRef SafeArray parameters on COM Events breaks execution, you can disable this code by adding the following configuration switch to your application config:
+
+```xml
+<appSettings>
+    <add key="Switch.System.Runtime.InteropServices.DoNotMarshalOutByrefSafeArrayOnInvoke" value="true" />
+</appSettings>
+```
+
+### Category
+Core