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

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

tests/pass-varying-lvalue-to-ref.ispc

@@ -4,8 +4,8 @@ export uniform int width() { return programCount; }
 void inc(uniform float * varying v) { ++(*v); }
 
 export void f_fu(uniform float ret[], uniform float aa[], uniform float b) {
-    uniform float foo[32];
-    for (uniform int i = 0; i < 32; ++i)
+    uniform float foo[2*programCount];
+    for (uniform int i = 0; i < 2*programCount; ++i)
         foo[i] = 10+i;
     int a = (int)aa[programIndex];
     inc(&foo[a]);