Netty Direct Buffer warning fix

When deploying Wildfly 8.x, you'll see this in the server.log:
```
INFO [io.netty.util.internal.PlatformDependent] Your platform does not provide complete low-level API for accessing direct buffers reliably. Unless explicitly requested, heap buffer will always be preferred to av
oid potential system unstability.
```
Following this into netty, here:
https://github.com/netty/netty/blob/master/common/src/main/java/io/netty/util/internal/PlatformDependent.java#L581
Down to here:
https://github.com/netty/netty/blob/netty-4.0.15.Final/common/src/main/java/io/netty/util/internal/PlatformDependent0.java#L82

We need access to sun.misc to see if direct buffers are available.
org.javassist should really be marked as optional given that this module is part of wildfly core.