Add some additional tests

tests/vector-varying-scatter-2.ispc

@@ -0,0 +1,17 @@
+
+export uniform int width() { return programCount; }
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    float aa = aFOO[programIndex]; 
+    float<4> a = { -1, -2, -3, -4 };
+    if (programIndex < 4)
+        a[3-programIndex] = aa;
+//CO    print("%\n%\n%\n%\n", a[0], a[1], a[2], a[3]);
+    int i = clamp(3-programIndex, 0, 3);
+//CO    print("%\n%\n", i, a[i]);
+    RET[programIndex] = a[i];
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = (programIndex < 4) ? 1+programIndex : -1;
+}