Mg v3.5

Changes

• Add support for Solaris/Illumos based UNIX systems. Tested on OmniOS
• Add Dockerfile and GitHub integration for container images
• Sync with mg upstream, OpenBSD 7.0, as of May 12, 2021
  • New replace-regexp function, for scripting
  • New dired function, dired-jump activated with C-x C-j
  • New dired-shell-command function for piping file to a command
  • New mgrc batch mode, mostly intended for regression testing
  • New command line option, -u mgrc, to specify startup mgrc file
  • Clarify markers in list-buffers output, more similar to GNU Emacs

Fixes

• Fix regression; lost path in status line while trying to open a file.
  Caused by a fix introduced in v3.4 to clear the status line on kill or
  switch buffer by name. A new fix has been made to handle both cases.
• Fix #10: replace deprecated signal functions with sigaction()
• Fix #11: segfault on disabled keybindings, --disable-ctags/cscope
• Fix various gcc build warnings