Description:
------------
For the sake of consistency and for the same reason that was noted in the source, 
let me quote it:
"as johannes suggesting use exceptioni to distinguish the error from a lua 
function return false"

Test script:
---------------
$l = new Lua();
try {
    $l->eval("invalid code");
} catch (LuaException $e) {
    echo $e->getMessage();
}

Expected result:
----------------
lua error: [string "line"]:1: '=' expected near 'code'

Actual result:
--------------
A warning is generated instead of a thrown exception