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.ispc

@@ -5,8 +5,8 @@ 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[40];
-    for (uniform int i = 0; i < 40; ++i)
+    uniform float x[programCount+5];
+    for (uniform int i = 0; i < programCount+5; ++i)
         x[i] = 0.;
     x[a] = 2;
     RET[programIndex] = x[4] + x[0] + x[5];