fixed problem with math in certain LC_NUMERIC locales.

thanks to wiebren for providing problem+solution.

libs/plugins/function.math.php

@@ -58,7 +58,7 @@ function smarty_function_math($params, &$smarty)
                 $smarty->trigger_error("math: parameter $key: is not numeric");
                 return;
             }
-            $equation = preg_replace("/\b$key\b/",$val, $equation);
+            $equation = preg_replace("/\b$key\b/", " \$params['$key'] ", $equation);
         }
     }