SPV_KHR_physical_storage_buffer/SPV: Add GL_EXT_buffer_reference_uvec2

Adds uvec2 <-> reference constructor support.
Switches from EXT to KHR for physical_storage_buffer.

glslang/Include/intermediate.h

@@ -275,6 +275,10 @@ enum TOperator {
     EOpConvUint64ToPtr,
     EOpConvPtrToUint64,
 
+    // uvec2 <-> pointer
+    EOpConvUvec2ToPtr,
+    EOpConvPtrToUvec2,
+
     //
     // binary operations
     //