syslogd: Enable repeated line compression for lines of any length.

Enable repeated line compression for lines of any length, instead of only
short lines. AFAICT repeated line compression was limited to short lines as
a RAM optimization, which made sense when karels added it in 1988, but no
longer. The penalty is a paltry 904B of RAM per file logged.

Reviewed by: rpaulo
MFC after: 32 days
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D4475