Do numeric comparison on db versions

Support MariaDB version 10.0 and forward, which previously did not appear to
be 'greater than' version 4.4 as in php '10.0' < '4.4'. Performing a split
by the dots allows php to perform a numeric comparison.

setup/inc/class.installer.php

@@ -83,7 +83,7 @@ class Installer extends SetupWizard {
         if(!$this->errors) {
             if(!db_connect($vars['dbhost'],$vars['dbuser'],$vars['dbpass']))
                 $this->errors['db']='Unable to connect to MySQL server. '.db_connect_error();
-            elseif(db_version()< $this->getMySQLVersion())
+            elseif(explode('.', db_version()) < explode('.', $this->getMySQLVersion()))
                 $this->errors['db']=sprintf('osTicket requires MySQL %s or better!',$this->getMySQLVersion());
             elseif(!db_select_database($vars['dbname']) && !db_create_database($vars['dbname'])) {
                 $this->errors['dbname']='Database doesn\'t exist';