Merge changes from origin/7.1

Merge changes from origin/7.1

d8b0b50 Always unlock the same session instance that was locked (#12481)
e6af0f0 Avoid leaking memory from inherited ThreadLocales. Fixes #12401
f7ee8fb Updated _trackMessageSize based on latest upstream version (#12468)
a24d391 Table ignores Container updates while painting (#12258)
7068d78 The colon in the calendar event caption is now also hideable. Fixes #12460
61dd8f7 Corrected typo in version variable (#12440)
476e0b8 Changed 'feature release' text to maintenance release (#12486)
faa2569 Updated browser versions
831747a Fix regression where empty RTA returns <br> (#12490)
cb8df75 Add deprecation message to unused constant
4c5bb0e Sets the locale in the test case. #12460
11cdf93 Excludes WeakValueMap from the serializable test #12401

Change-Id: Id7eeba06d14518c254ceb01e38e2441967932755