Consistently write loops over wxRegionIterator in the same way

Standardize on a single loop for all versions of it and prefer to use
"for" loops with the iterator increment directly in the loop statement
instead of using "while" loops with the increment somewhere inside the
loop, where it could be possibly skipped by a "continue" statement.

No real changes.

src/generic/grid.cpp

@@ -3678,13 +3678,12 @@ bool wxGrid::Redimension( wxGridTableMessage& msg )
 
 wxArrayInt wxGrid::CalcRowLabelsExposed( const wxRegion& reg, wxGridWindow *gridWindow ) const
 {
-    wxRegionIterator iter( reg );
     wxRect r;
 
     wxArrayInt  rowlabels;
 
     int top, bottom;
-    while ( iter )
+    for ( wxRegionIterator iter( reg ); iter; ++iter )
     {
         r = iter.GetRect();
         r.Offset(GetGridWindowOffset(gridWindow));
@@ -3724,8 +3723,6 @@ wxArrayInt wxGrid::CalcRowLabelsExposed( const wxRegion& reg, wxGridWindow *grid
 
             rowlabels.Add( row );
         }
-
-        ++iter;
     }
 
     return rowlabels;
@@ -3733,13 +3730,12 @@ wxArrayInt wxGrid::CalcRowLabelsExposed( const wxRegion& reg, wxGridWindow *grid
 
 wxArrayInt wxGrid::CalcColLabelsExposed( const wxRegion& reg, wxGridWindow *gridWindow ) const
 {
-    wxRegionIterator iter( reg );
     wxRect r;
 
     wxArrayInt colLabels;
 
     int left, right;
-    while ( iter )
+    for ( wxRegionIterator iter( reg ); iter; ++iter )
     {
         r = iter.GetRect();
         r.Offset( GetGridWindowOffset(gridWindow) );
@@ -3779,8 +3775,6 @@ wxArrayInt wxGrid::CalcColLabelsExposed( const wxRegion& reg, wxGridWindow *grid
 
             colLabels.Add( col );
         }
-
-        ++iter;
     }
 
     return colLabels;