STYLE: check autoPtr as plain bool instead of valid()

- cleaner code, more similarity with unique_ptr

  Now
      if (ptr)
      if (!ptr)

  instead
      if (ptr.valid())
      if (!ptr.valid())

applications/utilities/surface/surfaceMeshExport/surfaceMeshExport.C

@@ -277,7 +277,7 @@ int main(int argc, char *argv[])
         surf.cleanup(true);
     }
 
-    if (fromCsys.valid())
+    if (fromCsys)
     {
         Info<< "move points from coordinate system: "
             << fromCsys->name() << endl;
@@ -285,7 +285,7 @@ int main(int argc, char *argv[])
         surf.movePoints(tpf());
     }
 
-    if (toCsys.valid())
+    if (toCsys)
     {
         Info<< "move points to coordinate system: "
             << toCsys->name() << endl;