Update for net/haproxy to 1.4.21.

ChangeLog:

2012/05/21 : 1.4.21
    - MINOR: patch for minor typo (ressources/resources)
    - CLEANUP: fix typo in findserver() log message
    - DOC: cleanup indentation, alignment, columns and chapters
    - DOC: fix some keywords arguments documentation
    - MINOR: stats admin: allow unordered parameters in POST requests
    - MINOR: stats admin: use the backend id instead of its name in the form
    - BUG/MAJOR: trash must always be the size of a buffer
    - DOC: fix minor regex example issue and improve doc on stats
    - BUG/MAJOR: possible crash when using capture headers on TCP frontends
    - MINOR: config: disable header captures in TCP mode and complain
    - BUG/MEDIUM: balance source did not properly hash IPv6 addresses
    - CLEANUP: http: message parser must ignore HTTP_MSG_ERROR
    - CLEANUP: remove a few warning about unchecked return values in debug code
    - CLEANUP: http: remove unused http_msg->col
    - BUG/MINOR: http: error snapshots are wrong if buffer wraps
    - BUG/MAJOR: checks: don't call set_server_status_* when no LB algo is set
    - MINOR: proxy: make findproxy() return proxies from numeric IDs too
    - BUILD: http: stop gcc-4.1.2 from complaining about possibly uninitialized values
    - BUG/MINOR: stop connect timeout when connect succeeds

2012/03/10 : 1.4.20
    - BUG/MINOR: fix typo in processing of http-send-name-header
    - BUG/MEDIUM: correctly disable servers tracking another disabled servers.
    - BUG/MEDIUM: zero-weight servers must not dequeue requests from the backend
    - MINOR: halog: add some help on the command line    (cherry picked from commit 615674cdec067066a42f53f5d55628ab7b207e6c)
    - BUILD: fix build error on FreeBSD
    - BUG: queue: fix dequeueing sequence on HTTP keep-alive sessions
    - BUG: http: disable TCP delayed ACKs when forwarding content-length data
    - BUG: checks: fix server maintenance exit sequence
    - BUG/MINOR: stream_sock: don't remove BF_EXPECT_MORE and BF_SEND_DONTWAIT on partial writes
    - DOC: enumerate valid status codes for "observe layer7"
    - BUILD: make it possible to look for pcre in the default system paths

(morr)