Some logging fixes

These changes have fixed the following two issues for me:

1. Minecraft 1.7 recreates the latest.log file on server start, which makes tail fail. Tail appears to be still reading, but does not receive any of the new lines written to the new file with the same name. tail -F fixes that.
2. Logging format has changed since the release of 1.7.  Pre-1.7 would prefix log-entries with date and time. Now it is prefixed with a time-only-stamp between square brackets. This has broken the methods server_log_dots_for_lines and server_log_get_line, as well as log_line_get_time on which the former two depend. I have added an additional regex to identify the new format and deal with it appropriately.