Implement extensions GL_OVR_multiview and GL_OVR_multiview2

They are almost identical to the already supported GL_EXT_multiview

Test/spv.OVR_multiview.vert

@@ -0,0 +1,7 @@
+#version 330
+
+#extension GL_OVR_multiview : enable
+
+void main() {
+    gl_Position = vec4(gl_ViewID_OVR, 0, 0, 0);
+}