Clarify loop structure.

src/varscan.c

@@ -792,12 +792,11 @@ zaxis_compare(int zaxisID, int zaxistype, int nlevels, const double *levels, con
           const double *dlevels = zaxisInqLevelsPtr(zaxisID);
           if (dlevels && levels)
             {
-              int levelID;
-              for (levelID = 0; levelID < nlevels; levelID++)
-                {
-                  if (fabs(dlevels[levelID] - levels[levelID]) > 1.e-9) break;
+              for (int levelID = 0; levelID < nlevels; levelID++)
+                if (fabs(dlevels[levelID] - levels[levelID]) > 1.e-9) {
+                  differ = true;
+                  break;
                 }
-              if (levelID == nlevels) differ = false;
             }
 
           if (!differ && hasBounds)