Convert arrays to pointers in expressions like (a+5)

This was one instance of the C-style array/pointer duality that
was missed the first time around.

tests/array-pointer-duality-1.ispc

@@ -0,0 +1,15 @@
+
+export uniform int width() { return programCount; }
+
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    uniform float a[programCount];
+    for (unsigned int i = 0; i < programCount; ++i)
+        a[i] = aFOO[i];
+
+    RET[programIndex] = *(a + 2);
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 3;
+}