Catch exceptions by const-reference

Exceptions caught by value incur needless cost in C++, most of them can
be caught by const-reference, especially as nearly none are actually
used. This could allow compiler generate a slightly more efficient code.

modules/core/src/copy.cpp

@@ -729,7 +729,7 @@ static bool ipp_flip(Mat &src, Mat &dst, int flip_mode)
 
         CV_INSTRUMENT_FUN_IPP(::ipp::iwiMirror, iwSrc, iwDst, ippMode);
     }
-    catch(::ipp::IwException)
+    catch(const ::ipp::IwException &)
     {
         return false;
     }

modules/core/test/test_ds.cpp

@@ -1032,7 +1032,7 @@ void Core_SeqBaseTest::run( int )
                 cvClearMemStorage( storage );
         }
     }
-    catch(int)
+    catch(const int &)
     {
     }
 }
@@ -1200,7 +1200,7 @@ void Core_SeqSortInvTest::run( int )
             storage.release();
         }
     }
-    catch (int)
+    catch (const int &)
     {
     }
 }
@@ -1416,7 +1416,7 @@ void Core_SetTest::run( int )
             storage.release();
         }
     }
-    catch(int)
+    catch(const int &)
     {
     }
 }
@@ -1859,7 +1859,7 @@ void Core_GraphTest::run( int )
             storage.release();
         }
     }
-    catch(int)
+    catch(const int &)
     {
     }
 }
@@ -2121,7 +2121,7 @@ void Core_GraphScanTest::run( int )
             storage.release();
         }
     }
-    catch(int)
+    catch(const int &)
     {
     }
 }