Database: Raise the minimum required version of MySQL.

This raises the minimum version of MySQL required to run WordPress from 5.0 to 5.5.5.

MySQL 5.0 and 5.1 have long been unsupported and both reached end of life over 10 years ago. Combined usage for both versions sits at 0.4% of all WordPress sites.

Because 5.5 sits at just under 15% usage, 5.5 cannot be trimmed off at this time.

Of all sites running 5.5.x, 85% are running 5.5.5, and 100% are running 5.5.5 or higher. This makes it the logical landing spot.

Props johnbillion, sergeybiryukov, jorbin.
Fixes #60036.

git-svn-id: https://develop.svn.wordpress.org/trunk@57173 602fd350-edb4-49c9-b593-d223f7449a82

src/readme.html

@@ -52,7 +52,7 @@ <h2>Migrating from other systems</h2>
 <h2>System Requirements</h2>
 <ul>
 	<li><a href="https://secure.php.net/">PHP</a> version <strong>7.0</strong> or greater.</li>
-	<li><a href="https://www.mysql.com/">MySQL</a> version <strong>5.0</strong> or greater.</li>
+	<li><a href="https://www.mysql.com/">MySQL</a> version <strong>5.5.5</strong> or greater.</li>
 </ul>
 
 <h3>Recommendations</h3>

src/wp-includes/version.php

@@ -44,4 +44,4 @@
  *
  * @global string $required_mysql_version
  */
-$required_mysql_version = '5.0';
+$required_mysql_version = '5.5.5';