fix a bug(DetectorType never change)

changed line281 -> line220
Presentation:
because line 220 give the globle var mDetectorType,and in line 230 it will be compared with mDeteorType !!!  it will never be unequal ~
fix:
change mDetectorType(previous globle var) to a new local val tmpDetectorType

samples/android/face-detection/src/org/opencv/samples/facedetect/FdActivity.java

@@ -215,9 +215,9 @@ public class FdActivity extends Activity implements CvCameraViewListener2 {
         else if (item == mItemFace20)
             setMinFaceSize(0.2f);
         else if (item == mItemType) {
-            mDetectorType = (mDetectorType + 1) % mDetectorName.length;
-            item.setTitle(mDetectorName[mDetectorType]);
-            setDetectorType(mDetectorType);
+            int tmpDetectorType = (mDetectorType + 1) % mDetectorName.length;
+            item.setTitle(mDetectorName[tmpDetectorType]);
+            setDetectorType(tmpDetectorType);
         }
         return true;
     }