Bring hard-coded strings under control of i18n

[pander]

Please, bring the following hard-coded strings under control of i18n and notify i18n teams to provide translation for the following 16 strings.

Some translations already provide translation, but as a patch of the hardcoded strings in their localised release.

It concerns these lines in the following 4 files:

file wordpress/wp-admin/setup-config.php
line 55
 	wp_die( sprintf( /*WP_I18N_OLD_PHP*/'Your server is running PHP version %s but WordPress requires at least 4.3.'/*/WP_I18N_OLD_PHP*/, phpversion() ) );
line 58
 	wp_die( /*WP_I18N_OLD_MYSQL*/'Your PHP installation appears to be missing the MySQL extension which is required by WordPress.'/*/WP_I18N_OLD_MYSQL*/ );

file wordpress/wp-includes/wp-db.php
line 373-375
 			$this->bail(sprintf(/*WP_I18N_DB_CONN_ERROR*/"
 <h1>Error establishing a database connection</h1>
 <p>This either means that the username and password information in your <code>wp-config.php</code> file is incorrect or we can't contact the database server at <code>%s</code>. This could mean your host's database server is down.</p>
lines 377-379
 	<li>Are you sure you have the correct username and password?</li>
 	<li>Are you sure that you have typed the correct hostname?</li>
 	<li>Are you sure that the database server is running?</li>
lines 381-382
 <p>If you're unsure what these terms mean you should probably contact your host. If you still need help you can always visit the <a href='http://wordpress.org/support/'>WordPress Support Forums</a>.</p>
 "/*/WP_I18N_DB_CONN_ERROR*/, $dbhost), 'db_connect_fail');
line 428
 			return new WP_Error('invalid_db_prefix', /*WP_I18N_DB_BAD_PREFIX*/'Invalid database prefix'/*/WP_I18N_DB_BAD_PREFIX*/);
lines 460-461
 <h1>Can&#8217;t select database</h1>
 <p>We were able to connect to the database server (which means your username and password is okay) but not able to select the <code>%1$s</code> database.</p>
lines 463-465
 <li>Are you sure it exists?</li>
 <li>Does the user <code>%2$s</code> have permission to use the <code>%1$s</code> database?</li>
 <li>On some systems the name of your database is prefixed with your username, so it would be like <code>username_%1$s</code>. Could that be the problem?</li>
line 467
 <p>If you don\'t know how to setup a database you should <strong>contact your host</strong>. If all else fails you may find help at the <a href="http://wordpress.org/support/">WordPress Support Forums</a>.</p>'/*/WP_I18N_DB_SELECT_DB*/, $db, $this->dbuser), 'db_select_fail');
line 589
 			$error_str = sprintf(/*WP_I18N_DB_QUERY_ERROR_FULL*/'WordPress database error %1$s for query %2$s made by %3$s'/*/WP_I18N_DB_QUERY_ERROR_FULL*/, $str, $this->last_query, $caller);
line 591
 			$error_str = sprintf(/*WP_I18N_DB_QUERY_ERROR*/'WordPress database error %1$s for query %2$s'/*/WP_I18N_DB_QUERY_ERROR*/, $str, $this->last_query);
line 888
 			$this->print_error(/*WP_I18N_DB_GETROW_ERROR*/" \$db-get_row(string query, output type, int offset) -- Output type must be one of: OBJECT, ARRAY_A, ARRAY_N"/*/WP_I18N_DB_GETROW_ERROR*/);

file wordpress/wp-load.php
lines 49-50
 	$text_direction = /*WP_I18N_TEXT_DIRECTION*/"ltr"/*/WP_I18N_TEXT_DIRECTION*/;
 	wp_die(sprintf(/*WP_I18N_NO_CONFIG*/"There doesn't seem to be a <code>wp-config.php</code> file. I need this before we can get started. Need more help? <a href='http://codex.wordpress.org/Editing_wp-config.php'>We got it</a>. You can create a <code>wp-config.php</code> file through a web interface, but this doesn't work for all server setups. The safest way is to manually create the file.</p><p><a href='%ssetup-config.php' class='button'>Create a Configuration File</a>"/*/WP_I18N_NO_CONFIG*/, $path), /*WP_I18N_ERROR_TITLE*/"WordPress &rsaquo; Error"/*/WP_I18N_ERROR_TITLE*/, array('text_direction' => $text_direction));

file wordpress/wp-settings.php
line 109
 	die( sprintf( /*WP_I18N_OLD_PHP*/'Your server is running PHP version %s but WordPress requires at least 4.3.'/*/WP_I18N_OLD_PHP*/, phpversion() ) );
line 148
 	die( /*WP_I18N_OLD_MYSQL*/'Your PHP installation appears to be missing the MySQL extension which is required by WordPress.'/*/WP_I18N_OLD_MYSQL*/ );
line 290
 	wp_die(/*WP_I18N_BAD_PREFIX*/'<strong>ERROR</strong>: <code>$table_prefix</code> in <code>wp-config.php</code> can only contain numbers, letters, and underscores.'/*/WP_I18N_BAD_PREFIX*/);

Implementing this change by putting these strings under control of i18n will separate translation and functionality even more and ease the translation process.

[nacin]

These need to be hard-coded because we haven't yet loaded the translations at the point where we need these strings. See #7074 for an explanation on why they have the WP_I18N prefix and how translators should handle them.