Update wxPropertyGrid documentation

Completed documentation for topics marked as uncompleted.

include/wx/propgrid/propgriddefs.h

@@ -348,6 +348,7 @@ enum wxPG_MISC_ARG_FLAGS
     // Get/Store full value instead of displayed value.
     wxPG_FULL_VALUE                     = 0x00000001,
 
+    // Perform special action in case of unsuccessful conversion.
     wxPG_REPORT_ERROR                   = 0x00000002,
 
     wxPG_PROPERTY_SPECIFIC              = 0x00000004,

include/wx/propgrid/propgridiface.h

@@ -513,7 +513,7 @@ public:
     // category will be its own wxVariantList of wxVariant.
     // Use wxPG_INC_ATTRIBUTES to include property attributes as well.
     // Each attribute will be stored as list variant named
-    // "@@<propname>@@attr."
+    // "@<propname>@attr."
     wxVariant GetPropertyValues( const wxString& listname = wxEmptyString,
         wxPGProperty* baseparent = NULL, long flags = 0 ) const
     {