Correct a misspelling in log messages
Clean orphaned session file locks more aggressively

When using file-based sessions, lock files are orphaned once the session
is deleted through any call to tied(%session)->delete, such as logging
out.  These lock files continue to accumulate until the session cleaner
eventually picks them after a set age.

Over the course of even a relatively short, and common, 7 day max age
limit, the accumulated orphaned locks on a busy site (combined with all
the active sessions + locks) can bloat the size of the session directory
beyond the capacity of a standard ext3/4 filesystem directory entry.
Once this happens, sessions will start to fail sporadically with "No
space left on device" errors, despite plenty of disk space being
available.

Once a lock file is orphaned, it is safe to delete regardless of its
age.  Aggressively remove such locks whenever the session cleaner runs.

Arguably this should be handled inside Apache::Session when ->delete is
called.  Until then, the extra cleaning is simple to implement.
Merge branch '4.0/file-based-session-locks' into 4.0-trunk