Fix more tests for 32 and 64-wide execution.

tests/coalesce-1.ispc

@@ -5,7 +5,8 @@ export void f_f(uniform float RET[], uniform float aFOO[]) {
     uniform float * uniform buf = uniform new uniform float[32*32];
     for (uniform int i = 0; i < 32*32; ++i)
         buf[i] = i;
-
+    
+    assert(programIndex <= 64);
     RET[programIndex] = buf[64-programIndex];
 }