Log Message:
Update squid3 package to 3.5.15, security release.

* SQUID-2016:2 - Multiple Denial of Service issues in HTTP Response
  processing

    http://www.squid-cache.org/Advisories/SQUID-2016_2.txt

Changes to squid-3.5.15 (23 Feb 2016):

	- Bug 3870: assertion failed: String.cc: 'len_ + len <65536' in ESI::CustomParser
	- Fix multiple assertion on String overflows
	- Fix unit test errors on MacOS
	- Better handling of huge response headers. Fewer incorrect "Bug \ 
#3279" messages.
	- Log noise reduction for eCAP