Document wxListBox limitation concerning TAB characters.

TABs appear simply as a space under MSW (because we don't use LBS_USETABSTOPS
style there) but are aligned to (multiple of 8?) tab stops under GTK. It's not
clear which behaviour is actually preferable so for now just document the
inconsistency and advise people to use spaces instead.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72660 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/listbox.h

@@ -25,6 +25,10 @@
     performance nor from user interface point of view, for large number of
     items.
 
+    Notice that currently @c TAB characters in list box items text are not
+    handled consistently under all platforms, so they should be replaced by
+    spaces to display strings properly everywhere. The list box doesn't
+    support any other control characters at all.
 
     @beginStyleTable
     @style{wxLB_SINGLE}