Clarified connect to orign based on users@ question
doc: Update insert_(request|response)_via_str reference
TS-2246: cancel the trigger of CacheVC in openWriteCloseDataDone
Fixed indentation.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/trafficserver
Added section on avoiding thundering herd of requests
Bit of grammar changes
resolve merge conflict from TS-2089
LogObject.h doesn't need to #include SimpleTokenizer.h
White space formatting changes for new thundering herd section
TS-2255: TS should not flood printing after log space reach the limit

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-2256: Mem stats info is bad when enable reclaimable-freelist

1) Rename InkFreeList->count to InkFreeList->used, which could make
   it more readable.

2) Fix mem stats in reclaimable freelist -- I misunderstood the meaning
   of InkFreelist->count before.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-2259: Introduce failover hosts for logging system

This patch introduce failover hosts for collation host by using '|' delimiter
to extend <CollationHosts> tags in logs_xml.config.

Let me give an example:
<CollationHosts = "host1:5000|host2:5000|host3:6000, 209.131.52.129:6000"/>

In the example above, host2/host3 are failover hosts for host1. When host1
disconnected, log entries will be sent to host2, and then if host2 failed again,
log entries will be sent to host3 until host1 or host2 comes back.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-2260: Avoid flooding log when log host is down

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
Add CHANGES for TS-2259/TS-2260

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
Clean up some broken links
Remove extra : from import
TS-2257 Healthcheck plugin can stop watching some events.

The issue is related to the wonky garbage collection. This moves
all garbage collection to a dedicate "to-free list".
[TS-2261] Add config option to restore/elevate access to reading files by
root when loading plugins
Another attempt to fix formating of thundering herd section.