Add AUTOCOMP_SELECTION_CHANGE event for wxSTC

The SCN_AUTOCSELECTIONCHANGE notification was added in Scintilla 4.0 to
notify an application when a new item is selected in an autocompletion
or user list. However the version of Scintilla currently used is 3.7.2,
so this potentially useful notification is not available.

These changes allow an event corresponding to this notification to be
generated completely in the wxWidgets portion of wxSTC. If the Scintilla
library is ever updated to 4.0 or later, only one method should need to
be modified let Scintilla generate the event instead.

interface/wx/stc/stc.h

@@ -7876,6 +7876,10 @@ public:
 
     @event{EVT_STC_AUTOCOMP_SELECTION(id, fn)}
         Process a @c wxEVT_STC_AUTOCOMP_SELECTION event.
+    @event{EVT_STC_AUTOCOMP_SELECTION_CHANGE(id, fn)}
+        Process a @c wxEVT_STC_AUTOCOMP_SELECTION_CHANGE event.
+        @since 3.1.3
+
     @event{EVT_STC_CALLTIP_CLICK(id, fn)}
         Process a @c wxEVT_STC_CALLTIP_CLICK event.
     @event{EVT_STC_CHANGE(id, fn)}
@@ -7996,6 +8000,27 @@ public:
     @link wxStyledTextEvent::GetString GetString@endlink,
     @link wxStyledTextEvent::GetListCompletionMethod GetListCompletionMethod@endlink.
 
+    @c wxEVT_STC_AUTOCOMP_SELECTION_CHANGE
+
+    - Generated when items are highlighted in an autocompletion or user list.
+
+    - @link wxStyledTextEvent::GetPosition GetPosition@endlink will return the
+    position at which the list is being shown.
+
+    - For a user list, @link wxStyledTextEvent::GetListType GetListType@endlink
+    will return the list type. The list type is a value input in to the
+    @link wxStyledTextCtrl::UserListShow wxStyledTextCtrl::UserListShow@endlink
+    method when a user list is created.
+
+    - For an autocompletion list,
+    @link wxStyledTextEvent::GetListType GetListType@endlink will always return
+    zero.
+
+    - Valid event functions:
+    @link wxStyledTextEvent::GetListType GetListType@endlink,
+    @link wxStyledTextEvent::GetPosition GetPosition@endlink,
+    @link wxStyledTextEvent::GetString GetString@endlink.
+
     @c wxEVT_STC_CALLTIP_CLICK
 
     - Generated when a calltip has been clicked.
@@ -8488,7 +8513,8 @@ public:
         wxStyledTextCtrl::UserListShow @endlink method and can be used to
         distinguish lists if more than one is used.
 
-        This method is valid for @c wxEVT_STC_USERLISTSELECTION events.
+        This method is valid for @c wxEVT_STC_AUTOCOMP_SELECTION_CHANGE and
+        @c wxEVT_STC_USERLISTSELECTION events.
     */
     int  GetListType() const;
 
@@ -8636,6 +8662,7 @@ public:
         - @c wxEVT_STC_INDICATOR_RELEASE
         - @c wxEVT_STC_CALLTIP_CLICK
         - @c wxEVT_STC_AUTOCOMP_SELECTION
+        - @c wxEVT_STC_AUTOCOMP_SELECTION_CHANGE
         - @c wxEVT_STC_AUTOCOMP_COMPLETED
         - @c wxEVT_STC_MARGIN_RIGHT_CLICK
     */
@@ -8889,3 +8916,4 @@ const wxEventType wxEVT_STC_CLIPBOARD_COPY;
 const wxEventType wxEVT_STC_CLIPBOARD_PASTE;
 const wxEventType wxEVT_STC_AUTOCOMP_COMPLETED;
 const wxEventType wxEVT_STC_MARGIN_RIGHT_CLICK;
+const wxEventType wxEVT_STC_AUTOCOMP_SELECTION_CHANGE;