Fix OpenCL vectors that use "ext_vector_type" and add test

Author: ilcheese2

bindgen-tests/tests/expectations/tests/opencl_vector.rs

@@ -0,0 +1,9 @@
+typedef float float4 __attribute__((ext_vector_type(4)));
+typedef float float2 __attribute__((ext_vector_type(2)));
+
+float4 foo(float2 a, float2 b) {
+  float4 c;
+  c.xz = a;
+  c.yw = b;
+  return c;
+}

bindgen-tests/tests/headers/opencl_vector.h

@@ -1117,7 +1117,7 @@ impl Type {
 
                     TypeKind::Comp(complex)
                 }
-                CXType_Vector => {
+                CXType_Vector | CXType_ExtVector => {
                     let inner = Item::from_ty(
                         ty.elem_type().as_ref().unwrap(),
                         location,