allow build to proceed if either Qt or QScintilla is missing * configure.ac: Instead of aborting the configure script, set build_gui to "no" if Qt is missing. Don't abort configure script if QScintilla is missing. If QScintilla is available, define HAVE_QSCINTILLA. * file-editor-tab.cc, file-editor.cc, find-dialog.cc, lexer-octave-gui.cc: Surround file contents with #ifdef HAVE_QSCINTILLA. * main-window.cc (main_window::~main_window): Skip deletion of _file_editor if HAVE_QSCINTILLA is not defined. (main_window::new_file, main_window::open_file, main_window::focus_editor): Do nothing if HAVE_QSCINTILLA is not defined. (main_window::handle_entered_debug_mode, main_window::handle_quit_debug_mode): Skip operation on _file_editor if HAVE_QSCINTILLA is not defined. (main_window::construct): Skip creation of _file_editor and operations on it if HAVE_QSCINTILLA is not defined. * main-window.h (main_window::_file_editor): Omit data member from class if HAVE_QSCINTILLA is not defined.

--- a/libgui/src/main-window.h
+++ b/libgui/src/main-window.h
@@ -148,7 +148,9 @@
   void exit_callback (void);
 
   QTerminal *               _terminal;
+#ifdef HAVE_QSCINTILLA
   file_editor_interface *   _file_editor;
+#endif
   QMenu *                   _debug_menu;
 
   QAction *                 _debug_continue;