debug: Add debug_syslog_format setting

debug: Add debug_syslog_format setting

Without debug_hires_timestamp this produces a syslog style header
containing:

  "MON DD HH:MM:SS HOSTNAME PROGNAME[PID] "

With debug_hires_timestamp this produces a syslog style header
containing:

  "RFC5424-TIMESTAMP HOSTNAME PROGNAME[PID] "

All other settings are ignored.

This will be made visible via smb.conf in a subsequent commit.

This commit adds some simple hostname handling.  It avoids using
get_myname() from util.c because using that potentially pulls in all
manner of dependencies.  No real error handling is done.  In the worst
case debug_set_hostname() sets the hostname to a truncated version of
the given string.  Similarly, in an even weirder world,
ensure_hostname() sets the hostname to a truncation of "unknown".
Both of these are unlikely in all reasonable cases.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Ralph Boehme <slow@samba.org>