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-2.ispc

@@ -0,0 +1,17 @@
+
+export uniform int width() { return programCount; }
+
+
+export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
+    uniform int a[4][4][4];
+    for (uniform int i = 0; i < 4; ++i)
+        for (uniform int j = 0; j < 4; ++j)
+            for (uniform int k = 0; k < 4; ++k)
+                a[i][j][k] = 100*i+10*j+k;
+    
+    RET[programIndex] = *(a[2][3] + 1);
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 231;
+}