add a random number for round robin.
Merge pull request #500 from taoyuanyuan/robin

add a random number for round robin
add docs for ngx_http_sysguard_module

Chinese and English version.

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
add soreuseport option of socket, this feature come from linux 3.9
(http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=055dc21a1d1d219608cd4baac7d0683fb2cbbe8a).
you can set  "reuse_port on" in event block to open soreuseport option.
add docs for ngx_http_upstream_dynamic_module

English and Chinese versions.

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
fix grammar error in docs

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Merge pull request #509 from monadbobo/reuseport_fixed

add soreuseport option of socket.
Fix doc errors for sysguard and upstream_dynamic

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Merge pull request #508 from InfoHunter/master

add docs for sysguard module and upstream_dynamic module
bugfix: ngx_http_upstream_init_process will cause coredump while not have http block.
Feature: the "gzip_clear_etag" directive.
Merge pull request #515 from taoyuanyuan/random

bugfix: ngx_http_upstream_init_process will cause coredump
Merge pull request #514 from taoyuanyuan/etag

Feature: the "gzip_clear_etag" directive.
add doc for the "gzip_clear_etag" directive.
Merge pull request #516 from taoyuanyuan/doc

add doc for the "gzip_clear_etag" directive.
merged changes between nginx 1.4.7 and 1.6.1 except spdy
updated testcases
Merge pull request #517 from cfsego/merge-nginx-1.6.1

merged changes between nginx 1.6.1 and 1.4.7
dynamic_resolve.t: skip cases without Net::DNS::Nameserver
SPDY: fix connection leak

 * If ngx_http_spdy_finalize_connection() was called,
   ngx_http_spdy_body_filter(r, in) should return NGX_ERROR.
 * The write timer of spdy connection may be deleted.
Merge pull request #527 from chobits/spdy_bugfix

SPDY: fix connection leak