Add --log option to manual page (#1600)

Signed-off-by: W. Michael Petullo <mike@flyn.org>

bin/latexml

@@ -194,6 +194,7 @@ latexml [options] I<texfile>
                     by default it avoids this.
  --path=dir         adds to the paths searched for files,
                     modules, etc;
+ --log=file         specifies log file (default is file named after job name)
  --documentid=id    assign an id to the document root.
  --quiet            suppress messages (can repeat)
  --verbose          more informative output (can repeat)