Log Message:
logswan: update to 2.1.5.

Logswan 2.1.5 (2020-06-12)

- Switch the GEOIP2DIR example to point to '/var/db/dbip'
- Use CLOCK_REALTIME if CLOCK_MONOTONIC is not available
- Remove unneeded <sys/select.h> and <sys/types.h> includes
- Add missing <stddef.h> include
- Remove useless _POSIX_SOURCE define
- Remove useless _POSIX_C_SOURCE 199309L define
- Define _GNU_SOURCE in CMakeLists.txt to avoid cluttering source files
- No need to set HAVE_SECCOMP to 1, defining it is enough
- Remove some unneeded seccomp related includes