yahns 1.12.5 - proxy_pass + rack.hijack fixes

Hopefully the last of the 1.12.x series, this release
fixes a few minor bugs mainly needed for testing.

No upgrade should be necessary for non-proxy_pass users.

4 changes since v1.12.4 from the "maint" branch at
git://yhbt.net/yahns.git

      http_client: set state to :ignore before hijack callback
      test/test_client_expire: fix for high RLIMIT_NOFILE
      proxy_pass: do not chunk HTTP/1.0 with keep-alive
      proxy_pass: X-Forwarded-For appends to existing list

 lib/yahns/http_client.rb         |  6 +++---
 lib/yahns/proxy_http_response.rb |  8 ++++++--
 lib/yahns/proxy_pass.rb          |  5 ++++-
 test/test_client_expire.rb       | 13 +++++++++++--
 test/test_proxy_pass.rb          | 10 ++++++++++
 5 files changed, 34 insertions(+), 8 deletions(-)

Note: the current "master" branch (at commit 5e211ea003d2)
includes refactorings and new features not included in this
release.