Merge branch 'search-events'

Harmonize the behaviour across platforms.

Also fix ChangeValue() for this control.

And finally rename the events to use simpler names.

See https://github.com/wxWidgets/wxWidgets/pull/699

docs/changes.txt

@@ -178,6 +178,8 @@ All (GUI):
 - Add Set/GetFooter/Text/Icon() to wxRichMessageDialog (Tobias Taschner)
 - Add wxFloatingPointValidator::SetFactor().
 - Add "hint" property to wxSearchCtrl XRC handler.
+- Add wxEVT_SEARCH[_CANCEL] synonyms for wxSearchCtrl events.
+- Generate wxEVT_SEARCH on Enter under all platforms.
 
 wxGTK: