Support for the PROXY protocol

This will be implemented as an attribute called proxy-protocol under each of the listeners. If this is set to true then the listener will be wrapped by the Undertow proxy protocol implementation. This wrapper reads the proxy protocol header from the stream, before handing off the connection to the normal listener implementation.

This information will be used by any part of the request processing that requests the remote clients IP address, including access logging and calls to javax.servlet.ServletRequest#getRemoteAddr().

This will be supported for HTTP, HTTPS, but not AJP.

This does not involve adding support for acting as a load balanacer using the proxy protocol. The proxy protocol is connection based rather than request based, so there would be basically zero code reuse between the existing proxy and any java implementation of a proxy.

Tests will be created in the Wildfly test suite that adds both a HTTP and HTTPS listener with this attribute set to true. Using a raw socket a proxy protocol connection will be established, and a HTTP request sent. A servlet will be installed in Wildfly that sends back the reported remote address, and these will be compared to what was sent in the proxy protocol header.

Core comprehensive tests for proxy protocol support are present in the Undertow test suite, the WildFly test suite will just contain smoke tests to make sure the configuration is working as expected.