GL_ACTIVE_ATTRIBUTE_MAX_LENGTH and ACTIVE_ATTRIBUTES

Some of the constant values declared in GL20.kt are wrong:

```
ACTIVE_ATTRIBUTES = 0x8B86
ACTIVE_ATTRIBUTE_MAX_LENGTH = 0x8B87
```

should be:

```
ACTIVE_ATTRIBUTES = 0x8B89
ACTIVE_ATTRIBUTE_MAX_LENGTH = 0x8B8A
```