Speedup multilog

Here's 3 commits for speedups in multilog. Not earth-shattering, but significant.

Using gprof, the biggest bottleneck was in doit(). Tested against various lengths of 3,000,000 log messages each, before and after times spent in doit():

msg
len          before        after
-------      ----------     ---------
20            0.84s      0.65s
140          4.36s      2.43s
1000      27.98s     16.31s
2000      71.08s     58.53s