[ticket/15097] Add PHP version to Board statistics

The ACP main page shows the phpBB version and the database version,
but didn't show the PHP version.

With this change the PHP version is displayed as part of the
Board statistics.

PHPBB3-15097

phpBB/adm/style/acp_main.html

@@ -167,6 +167,10 @@
 		<td>&nbsp;</td>
 	<!-- ENDIF -->
 	</tr>
+        <tr>
+        <td>{L_PHP_VERSION}{L_COLON} </td>
+        <td><strong>{PHP_VERSION}</strong></td>
+    </tr>
 	<!-- ENDIF -->
 	</tbody>
 	</table>

phpBB/includes/acp/acp_main.php

@@ -569,6 +569,7 @@ class acp_main
 			'S_TOTAL_ORPHAN'	=> ($total_orphan === false) ? false : true,
 			'GZIP_COMPRESSION'	=> ($config['gzip_compress'] && @extension_loaded('zlib')) ? $user->lang['ON'] : $user->lang['OFF'],
 			'DATABASE_INFO'		=> $db->sql_server_info(),
+            'PHP_VERSION'       => PHP_VERSION,
 			'BOARD_VERSION'		=> $config['version'],
 
 			'U_ACTION'			=> $this->u_action,

phpBB/language/en/acp/common.php

@@ -373,6 +373,7 @@ $lang = array_merge($lang, array(
 	'NUMBER_USERS'		=> 'Number of users',
 	'NUMBER_ORPHAN'		=> 'Orphan attachments',
 
+    'PHP_VERSION'       => 'PHP version',
 	'PHP_VERSION_OLD'	=> 'The version of PHP on this server (%1$s) will no longer be supported by future versions of phpBB. The minimum required version will be PHP %2$s. %3$sDetails%4$s',
 
 	'POSTS_PER_DAY'		=> 'Posts per day',