Allow unconfined domains to use syslog capability

When an unconfined_t root user runs dmesg, the kernel complains with
this message in its logs (when SELinux is in enforcing mode):

  dmesg (16289): Attempt to access syslog with CAP_SYS_ADMIN but no
  CAP_SYSLOG (deprecated).

audit.log contains following AVC:

  avc:  denied  { syslog } for  pid=16289 comm="dmesg" capability=34
  scontext=unconfined_u:unconfined_r:unconfined_t
  tcontext=unconfined_u:unconfined_r:unconfined_t tclass=capability2
Module version bump for unconfined syslog cap from Nicolas Iooss.
Always use the unknown permissions handling build option.

This compile-time feature is in the minimum-required checkpolicy/checkmodule
for building the policy, so it should always be used.