* backport a slightly modified subshell patch to stable 4.8.15
  (see ticket: https://www.midnight-commander.org/ticket/2742)
* enable subshell support by default

Signed-off-by: Dirk Brenken <dirk@brenken.org>

bump version to 4.8.15
fix charset / utf-8 support
fix different warnings during startup
merge all configuration files in /etc/mc
enable internal editor & charset support by default

Signed-off-by: Dirk Brenken <dirk@brenken.org>

- add & reorder new compile time options with help text
- all options are disabled by default, to reduce space req.
- remove invalid mc configure options
- fix broken makefile logic to enable/disable mc options

Signed-off-by: Dirk Brenken <dibdot@gmail.com>

Signed-off-by: Dirk Brenken <dibdot@gmail.com>