Add some additional tests

tests/ptr-int-null.ispc

@@ -0,0 +1,13 @@
+
+export uniform int width() { return programCount; }
+
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    uniform int a = 1;
+    uniform int * uniform b = 0;
+    RET[programIndex] = (b == NULL && b == 0 && 0 == b) ? 1 : 0;
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1;
+}