Add support for loading external lexers to wxStyledTextCtrl

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

Closes #17480.

include/wx/stc/stc.h

@@ -4773,6 +4773,9 @@ public:
     // Set the lexing language of the document based on string name.
     void SetLexerLanguage(const wxString& language);
 
+    // Load a lexer library (dll / so).
+    void LoadLexerLibrary(const wxString& path);
+
     // Retrieve a 'property' value previously set with SetProperty.
     wxString GetProperty(const wxString& key);
 
@@ -4787,6 +4790,9 @@ public:
     // Retrieve the number of bits the current lexer needs for styling.
     int GetStyleBitsNeeded() const;
 
+    // Retrieve the lexing language of the document.
+    wxString GetLexerLanguage() const;
+
     // For private communication between an application and a known lexer.
     void* PrivateLexerCall(int operation, void* pointer);