IE8 doesn't support the brackets notation for getting a character in CHAR64

IE8 (not tested with other versions) does not support the following code:
```
var bou = "abcdef"
var char = bou[3]  // returns "undefined" with IE
```
The correct syntax is:
```
var bou = "abcdef"
var char = bou.charAt(3) // returns "d" with all browsers
```

This causes CGXP's issue camptocamp/cgxp#417