sysklogd: upgrade 2.4.4 -> 2.5.0

sysklogd: upgrade 2.4.4 -> 2.5.0

Changes
=======
- Issue #59: initial port to NuttX, contributed by Xiaomi
- Issue #61: add support for '-c' and '-cc' to disable log compression.
  A single '-c' disables compression for pipes, another '-c' (or '-cc')
  disables compression for all other log targets
- The default 'syslog.conf' now logs debug messages again (disabled in
  v2.4.0) due to problems (confusion) reported in the field
- Dropped not recommended 'KillMode=process' from systemd unit file

Fixes
========
- Issue #60: document how to set side-wide permissions on log files
- Issue #62: early log messages lost when running under systemd, found
  by Wind River Systems, including initial fix

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>