Add support for "hint" property in wxTextCtrl XRC handler.

It is convenient to allow specifying the hints directly in the resources.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76628 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/overviews/xrc_format.h

@@ -1840,6 +1840,8 @@ No additional properties.
     Initial value of the control (default: empty).}
 @row3col{maxlength, integer,
     Maximum length of the text which can be entered by user (default: unlimited).}
+@row3col{hint, @ref overview_xrcformat_type_text,
+    Hint shown in empty control (new since wxWidgets 3.0.1).}
 @endTable