Raise MySQL requirement to 5.5.3

Problem/Motivation

Currently Drupal requires MySQL 5.1.21 but we should increase that requirement to at least 5.5.3 (released in 03/2010) in order to be able to use utf8mb4 encoding by default. However, to also force a more secure (and mature) 5.5 version, @crell advocated to raise it even further to 5.5.37, released on 2014-03-27 and present in most current Linux distros.

See #1314214: MySQL driver does not support full UTF-8 (emojis, asian symbols, mathematical symbols).

Versions of MySQL in shipping distributions:

* Debian wheezey: 5.5.41-0+wheezy1
* OpenSuse: 5.5.42
* Ubuntu 12.04 LTS: 5.5.41
* RedHat EL 5.11: 5.5.37
* CentOS 5: 5.5.37

Hosting utilities:
cPanel & WHM 11.44 (2014-05) require MySQL 5.5

Hosts:
Rackspace offers 5.6 by default while still supporting 5.1

Proposed resolution

Instead of only increasing the minimum version of MySQL it was decided that we better check for the feature in question to be available by doing a "set names utf8mtb4". This is more self explaining and allows for the fact that the different databases that this driver supports might have added this feature in different versions. Might have as according to comment #32, the feature divergence between MySql and MariaDb only started as of version 5.6. so in the future a pure version check might prove not usable.

Remaining tasks

None

Beta phase evaluation