Motivation:
The STOMP decoder used to fail when parsing a frame with no content-length
and a body split across multiple packets.
Modifications:
Support contentLength of -1 (indicating indeterminate length) and added a
check to getContentLength. Moved the NUL byte searching from the
readHeaders() method out to the main decoder loop.
Result:
A STOMP frame can be properly parsed even if it's missing the
content-length header and the NUL byte is in a later packet.
