Use symbolic constants instead of numeric ones to represent masks filtering window style flags in wxPG.

src/propgrid/propgrid.cpp

@@ -327,10 +327,12 @@ bool wxPropertyGrid::Create( wxWindow *parent,
     style |= wxWANTS_CHARS;
 
     wxControl::Create(parent, id, pos, size,
-                      style | wxScrolledWindowStyle,
+                      (style & wxWINDOW_STYLE_MASK) | wxScrolledWindowStyle,
                       wxDefaultValidator,
                       name);
 
+    m_windowStyle |= (style & wxPG_WINDOW_STYLE_MASK);
+
     Init2();
 
     return true;