gui: Add select all menu (Bug #41797) * libgui//qterminal/libqterminal/QTerminal.h: Add selectAll popup menu and virtual function. * libgui/qterminal/libqterminal/unix/QUnixTerminalImpl.cpp,h: Add selectAll function. * libgui/qterminal/libqterminal/unix/TerminalView.cpp,h: add selectAll function. * libgui/qterminal/libqterminal/win32/QWinTerminalImpl.cpp,h: Add selectAll function. * libgui/src/documentation-dock-widget.cc,h: Add selectAll function. * libgui/src/files-dock-widget.cc,h: Add selectAll function. * libgui/src/history-dock-widget.cc,h: Add selectAll function. * libgui/src/m-editor/file-editor-tab.cc,h: Add select_all function and signal. * libgui/src/m-editor/file-editor.cc,h: Add request_selectall and selectAll function, add Edit->select all menu. * libgui/src/main-window.cc: add selectAll function, selectAll menu. * libgui/src/octave-dock-widget.cc,h: Add virtual selectAll function and connect to mainwindow selectall signal. * libgui/src/qtinfo/webinfo.cc,h: Add selectAll function. * libgui/src/workspace-view.cc,h: Add selectAll function.

--- a/libgui/qterminal/libqterminal/unix/TerminalView.h
+++ b/libgui/qterminal/libqterminal/unix/TerminalView.h
@@ -416,6 +416,11 @@
      */
     void pasteSelection();
 
+    /**
+     * selects all content 
+     */
+    void selectAll();
+
 	 /**
 	 * Causes the widget to display or hide a message informing the user that terminal
 	 * output has been suspended (by using the flow control key combination Ctrl+S)