added the attribute 'id' for upstream server

This attribute can be specified by user. It may be useful for
session sticky load balance or other hash based methods.
added the attribute of id for round robin
initialized the id to be null string
fixed the id prameter
removed the macro NGX_HTTP_UPSTREAM_ID check expression
increased the NGX_NUMBER_MAJOR to 2
added the check of the end space of the line
fixed coding style
Merge pull request #115 from yaoweibin/server_id

added the attribute 'id' for upstream server
Merge pull request #142 from yaoweibin/fixed_style2

fixed the coding style
allow writing syslog address with domain or hostname
add a test case
支持识别Safari 配置
Merge pull request #144 from cfsego/syslog

allow writing syslog address with domain or hostname
fixed an error
Merge pull request #145 from dinic/user_agent

支持识别Safari 配置
fix bug for dso module (start nginx and no dso block, and then add dso block and dso module, at last reload nginx, nginx will reload failed).
Merge pull request #146 from monadbobo/dso_fix3

fix bug for dso module when reloading nginx
upstream check: fix the check status "down" for a single server.

If a single server is marked down by upstream check module, it will
return 502 directly before.

This fix can use the backup server eventually for sure in the above
case.
Fixed segmentation fault in ngx_show_dso_directives() and ngx_is_dynamic_module().if we don't set dso block in nginx config, ctx->module is NULL, and then exec nginx -v, -m or -l will casuse nginx coredump.