Fix a number of tests to work correctly with 32/64-wide targets.

Still to be reviewed/fixed: tests/test-*, tests/[cfrs]*

tests/array-scatter-unif-2.ispc

@@ -4,9 +4,8 @@ export uniform int width() { return programCount; }
 
 export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
     float a = aFOO[programIndex];
-    uniform float x[100];
-    // HACK to avoid @llvm.memset...
-    for (uniform int i = 0; i < b*20; ++i)
+    uniform float x[2*programCount];
+    for (uniform int i = 0; i < 2*programCount; ++i)
         x[i] = 0;
     
     x[2*(a-1)] = b;