Add support for loading external lexers to wxStyledTextCtrl

Implement Scintilla DynamicLibraryImpl and generate LoadLexerLibrary() and
GetLexerLanguage().

Closes #17480.

interface/wx/stc/stc.h

@@ -6031,6 +6031,11 @@ public:
     */
     void SetLexerLanguage(const wxString& language);
 
+    /**
+        Load a lexer library (dll / so).
+    */
+    void LoadLexerLibrary(const wxString& path);
+
     /**
         Retrieve a 'property' value previously set with SetProperty.
     */
@@ -6053,6 +6058,11 @@ public:
     */
     int GetStyleBitsNeeded() const;
 
+    /**
+        Retrieve the lexing language of the document.
+    */
+    wxString GetLexerLanguage() const;
+
     /**
         For private communication between an application and a known lexer.
     */