Changes 3.5.5:
* Portability: migrate auto_ptr to C++11 unique_ptr
* Portability: Define nullptr if not provided
* Cleanup: sync ModSelect.cc and ModSelectWin32.cc
* Fix segmentation fault inside Adaptation::Icap::Xaction::swanSong
* Fix "Not enough space to hold server hello message" error message
* Bug 4132: regression in short_icon_urls with global_internal_static on
* Prevent unused ssl_crtd helpers being run
* Docs: fix debug output on https_port context failure
* HTTP/2: publish RFC 7540
* Fix incorrect use of errno in various libcomm.la places
* Bug 4236: SSL negotiation error of 'success'
* Fix signal.h usage to resolve compiler warning
* Bug 3930: assertion 'connIsUsable(http->getConn())'
* Fix missing external ACL helper notes
* Bug 4238: assertion Read.cc:205: "params.data == data"
* Docs: remove 4.0-only info added by rev.13823
* comm_connect_addr on failures returns Comm:OK
* Docs: shuffle SMP specific options to the top of squid.conf
* CacheMgr: display 'client_db off' instead of 0 clients accessing cache
* Fix assertion errorpage.cc:600: "entry->isEmpty()"
* Fix assertion MemBuf.cc:380: "new_cap > (size_t) capacity" in SSL I/O buffer

(adam)