Mg v3.6

Changes

• Add support for exuberant/universal Ctags tags file format
• Add support for M-, to pop-tag-mark, like GNU Emacs
• Sync with mg upstream, OpenBSD 7.2, as of April 10 2023
  • Drop trailing whitespace on RET (c-mode)
  • Add zap-to-char and zap-up-to-char, binding the former to M-z
  • Change visit-tags-table to immediately load tags file
• Add support for --without-docs to skip installation of files to
  /usr/share/doc/mg, including the manual
• Install gzipped tutorial in /usr/share/mg/, for built-in help

Fixes

• Sync with mg upstream, OpenBSD 7.2, as of March 26 2023
  • Fix dobeep_msgs() usage, does not support format strings, this may
    have caused unexpected crashes for some operations, e.g. goto line
    that does not exist
  • Fix memleaks and possible crashes in ctags support
  • Fall back to /bin/sh if $SHELL is undefined
  • Use basename of argv[0] instead of hard coding "sh"
• Fix #17: typos in *quick* help buffer, also replace duplicate undo
  with mark command instead
• Fix #18: revert-buffer crash on macOS