use QScintilla instead of QTextEdit for new terminal widget * command-widget.cc (ctor): pass qobj to console; (insert_interpreter_output): just append output message to console text; (console::console): initialize QScintilla, remove obsolete document; (console::new_command_line): append new line, add prompt, remember current cursor pos for later use, append possibly given command string; (console::accept_command_line): just get last line, and append a new line; (console::append_block): removed; (console::append_string): new function appending a string and moving cursor to the end; (console::keyPressEvent): process QsciScintilla::keyPressEvent * command-widget.h: include Qsci/qsciscintilla.h, console inherits from QsciScintilla and gets oct_qobj for later use, new function append_string, new class variable m_command_position for storing the begin of the active command line

Things to do before making a release:

  * Update the version number and release date in configure.ac.

  * Update the OCTAVE_API_VERSION number in configure.ac.

  * Update version number and release year in CITATION.

  * Update the etc/NEWS.N.md file corresponding to the major release
    number N.  Include release date in Summary header.

  * Update the NEWS-<VERSION>.html, index.in, news.in, and download.in
    files for the web site.

  * Copy tarballs to ftp.gnu.org.

  * Post a release announcement to the help@octave.org and
    info-gnu@gnu.org lists.

  * Update https://wiki.octave.org/Release_History page.