Add support for broadcast(), rotate(), and shuffle() stdlib routines

tests/rotate-2.ispc

@@ -0,0 +1,13 @@
+
+export uniform int width() { return programCount; }
+
+export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
+    int a = aFOO[programIndex]; 
+    uniform int delta = b - 6; // -1
+    int rot = rotate(a, delta);
+    RET[programIndex] = rot;
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1 + (programIndex + programCount - 1) % programCount;
+}