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

tests/rotate.ispc

@@ -0,0 +1,12 @@
+
+export uniform int width() { return programCount; }
+
+export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
+    int a = aFOO[programIndex]; 
+    int rot = rotate(a, 2);
+    RET[programIndex] = rot;
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1 + (programIndex + 2) % programCount;
+}