TS-2005: fix a race that may do two send_msg in cache read.
TS-2166: Response header to ua has two "Content-Range" field

1) Update the value of "Content-Range" field if it exists
2) Remove "Content-Range" field if ua sends multi-range request
TS-2165: Introduce cluster-wide logging stats

With this patch, we can see the logging status of whole cluster.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
Change-Id: I8c6cb40df05cced092b3326ab6a75e7bdfb33926
TS-2005: correct session config parameters registeration
TS-977 RecCore: refine P_RecCore.i and rename it to P_RecCore.cc

The suffix of P_RecCore.i is weird for us:
1) cscope can't find the function definition in it by default.
2) using *.i suffix usually indicates that there are something
   bad in design. We can share the code gracefully if spliting the
   function/class carefully.

Let's refine the code so that we can rename it to P_RecCore.cc safely.
BTW, remove an useless file: ./iocore/utils/diags.i.

I have noticed that there are several test_*.i files which is not so
important for us, just keep it as it is.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
Signed-off-by: Zhao Yongming <ming.zym@gmail.com>