Update libevent to 1.4.12-stable-1

[Rico Tzschichholz]

Please update libevent package to 1.4.12-stable-1.
This is a bugfix release, so I hope it is still possible to include it.

http://packages.debian.org/source/squeeze/libevent

Changes in 1.4.12-stable:
  o Try to contain degree of failure when running on a win32 version so heavily firewalled that we can't fake a socketpair.
  o Fix an obscure timing-dependent, allocator-dependent crash in the evdns code.
  o Use __VA_ARGS__ syntax for varargs macros in event_rpcgen when compiler is not GCC.
  o Activate fd events in a pseudorandom order with O(N) backends, so that we don't systematically favor low fds (select) or earlier-added fds (poll, win32).
  o Fix another pair of fencepost bugs in epoll.c. [Patch from Adam Langley.]
  o Do not break evdns connections to nameservers when our IP changes.
  o Set truncated flag correctly in evdns server replies.
  o Disable strict aliasing with GCC: our code is not compliant with it.