* 2.3:
bumped Symfony version to 2.3.40
set s-maxage only if all responses are cacheable
updated VERSION for 2.3.39
update CONTRIBUTORS for 2.3.39
updated CHANGELOG for 2.3.39
Improved the "branch" row of the PR table
Fix typos #18090 1. PHPs session design to PHP's session design 2. Symfony HttpKernel offers to Symfony's HttpKernel offers 3. in which case it it should to in which case it should
Fix for Isssue #18091
replace perfom by perform
minor #18088 Fix typo for profiler
