Update to 2.46

Upstream changes:
2.46    2015-08-05

- Really make the per-thread locking in the Syslog output work. Based on a
  patch by David Schweikert. GitHub #9.

2.45    2015-06-14

- Don't include threads and threads::shared in list of dependencies. This is
  only needed for Log::Dispatch::Syslog and is loaded at runtime as needed
  (which has its own issues but ...). Reported by Kent Fredric. RT #103392.

(wen)