redirect stdout and stderr into experimental terminal widget * command-widget.cc (command_widget): open temp files for redirecting stdout and stderr, setup a file system watcher for signals on changes to these files; (~command_widget): close and remove the temp. files; (insert_interpreter_output): use the style as second argument (print_stream): add new contents of temp. files for stdout and stderr to the end of the terminal contents; (notice_settings): set the terminal preferences to the new lexer of the console; (console): create and set new lexer; (new_command_line): use prompt style for the prompt; (execute_command): use second command line argument for the style; (append_string): use style as second argument and style the added text accordingly; * command-widget.h (console) append_string with second argument for style, (command_widget): now with destructor, new method print_stream, insert_interpreter_output with second argument for style, new class variables for temp. file descriptors and file system watcher * console-lexer.cc/h: new lexer derived from QScintillas default lexer for styling the terminal output, styles used so far: Default, Error, and Prompt * gui-preferences-cs.h: new constants for error and prompt colors * libgui/src/module.mk: new files console_lexer.cc/h * qt-interpreter-events.cc (display_exception): interpreter_output_signal with second argument for the style, here Error style * qt-interpreter-events.h: interpreter_output_signal with second argument for the style * terminal-dock-widget.h: interpreter_output_signal with second argument for the style