Have page-specific splitter setup flags in order to fix bug that caused splitter change in one page to affect others. Also fixed a regression in splitter auto-centering.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62374 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/propgrid/propgridpagestate.h

@@ -738,6 +738,12 @@ protected:
 
     unsigned char               m_vhCalcPending;
 
+    /** True if splitter has been pre-set by the application. */
+    bool                        m_isSplitterPreSet;
+
+    /** Used to (temporarily) disable splitter centering. */
+    bool                        m_dontCenterSplitter;
+
 private:
     /** Only inits arrays, doesn't migrate things or such. */
     void InitNonCatMode();