release: Update NEWS for 2.99.3 release

NEWS

@@ -1,3 +1,52 @@
+===============================================================================
+Gtk# 2.99.3 - 2014-06-06
+===============================================================================
+
+Gtk# 2.99.3 is a beta release of C# bindings for GTK 3.x.
+
+This version of Gtk# provides bindings for the API exposed by these libraries:
+  * cairo 1.10.0
+  * glib 2.28.0
+  * pango 1.28.3
+  * atk 1.32.0
+  * gdk-pixbuf 2.22.1
+  * gtk+ 3.0.0
+
+There is no API stability guarantee for now, but we try to keep breaking
+changes to a minimum.
+
+This version of Gtk# can be installed in parallel with Gtk# 2.x, and should not
+have any impact on applications using Gtk# 2.x.
+
+New features and enhancements
+-----------------------------
+
+  * Windows installer: this is the first release of a Gtk# Windows installer
+    with GTK+ 3.x. It includes 32-bit native binaries of GTK+ 3.6.4, provided
+    at http://www.gtk.org/download/win32.php
+ * generator: Add support for fixed length arrays as method parameters
+ * build: Add a pkg-config file for gdk-sharp-3.0
+ * Add samples to show the Spinner widget, and to demonstrate CSS theming
+
+Changes
+-------
+
+  * generator: Create a directory for each namespace of generated code
+  * cairo: Remove FormatStrideForWidth and PathExtents methods from Context
+  * glib: Add GVariant to fundamental types and allow conversion to and from
+    GValue
+
+Bug fixes
+---------
+
+  * Various fixes to build on Windows with MinGW and the .NET compiler
+  * generator: Fix generation of SetGValue method
+  * generator: Add new keyword to GType property if it hides parent
+  * generator: Fix handle being passed when type is a struct
+  * generator: Fix signature of static method overloads
+  * gtk: Add ListStore.SetValue overload for long type
+
+
 ===============================================================================
 Gtk# 2.99.2 - 2013-12-04
 ===============================================================================