Reactor: Add UInt4 constructors taking UInt

Odd that these don't exist already.

Change-Id: I018dc4eb5144cb4c359c790aadabc35516bdd745
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31430
Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Shader/VertexProgram.cpp b/src/Shader/VertexProgram.cpp
index 67307ef..b3f81a0 100644
--- a/src/Shader/VertexProgram.cpp
+++ b/src/Shader/VertexProgram.cpp
@@ -92,7 +92,7 @@
 		{
 			if(state.textureSampling)
 			{
-				vertexID = Int4(index);
+				vertexID = Int4(Int(index));
 			}
 			else
 			{