Added proxy_upstream_tries directive, which can limit
proxy_next_upstream retry times. This directive can work in
main/server/http/location config, and is disabled by
default(default behavior is to try ALL upstreams). Partial code is
forked from patch: https://gist.github.com/shai-d/5446961.
Added decode base64 variable
Added md5 variable as a function
Limit proxy/memcached/fastcgi/scgi/uwsgi upstream tries times.
Merge branch 'master' into limit_upstream_tries
Changed the variable's name from md5_ to encode_md5_
fixed a bug of trim module.
add test cases for limit_upstream_tries
disable limit_upstream_tries when xxx_upstream_tries is set to 0.
Merge pull request #322 from supertcy/limit_upstream_tries

Limit proxy/memcached/fastcgi/scgi/uwsgi upstream tries times
nginx-tfs new features and bug-fixs.

1. fix nginx do not close connection bug
2. use readv2 if read from start
3. write failed now retry ns instead of ds
4. fix do not remove dirty block cache when stat large file bug
5. fix pread custom file bug when read offset is larger than 2 times of segment's start offset
6. fix rc timer bug
7. fix write failed bug when data to write is in memory
8. fix select cluster bug
9. add Content-type response header
Merge pull request #329 from zhcn381/upstream2

nginx-tfs new features and bug-fixs.
Merge pull request #325 from taoyuanyuan/point

fixed a bug of trim module.
Merge pull request #324 from flygoast/master

add 'raw_uri' built-in variable for original request URI but without arguments.
modify variables' name
Merge pull request #319 from yzprofile/unbase64

Added decode base64 variable
Don't process the encoding response in foot filter module
Merge pull request #333 from yaoweibin/fix_filter_accept_encoding

it looks good to me
fixed an problem that it may don't pass the request header

When the client_body_postpone_size is specified to be 0, it doesn't
pass the headers before receving any request body.
Merge pull request #334 from yaoweibin/fix_zero_size

fixed an problem that it may don't pass the request header