PROTON-1687/PROTON-1726: Fix crash when using PN_TRACE_RAW - Corrected unsigned subtraction mess.
PROTON-1687/PROTON-1726: Fix crash when using PN_TRACE_RAW
- Corrected unsigned subtraction mess.

apache/qpid-proton,astitcher/qpid-proton,gemmellr/qpid-proton,astitcher/qpid-proton,ssorj/qpid-proton,alanconway/qpid-proton,alanconway/qpid-proton,astitcher/qpid-proton,kgiusti/qpid-proton,ssorj/qpid-proton,kgiusti/qpid-proton,kgiusti/qpid-proton,gemmellr/qpid-proton,apache/qpid-proton,ChugR/qpid-proton,apache/qpid-proton,gemmellr/qpid-proton,gemmellr/qpid-proton,ssorj/qpid-proton,apache/qpid-proton,kgiusti/qpid-proton,astitcher/qpid-proton,ChugR/qpid-proton,gemmellr/qpid-proton,alanconway/qpid-proton,alanconway/qpid-proton,ChugR/qpid-proton,ssorj/qpid-proton,alanconway/qpid-proton,astitcher/qpid-proton,ChugR/qpid-proton,kgiusti/qpid-proton,apache/qpid-proton,gemmellr/qpid-proton,ssorj/qpid-proton,ssorj/qpid-proton,alanconway/qpid-proton,ChugR/qpid-proton,astitcher/qpid-proton,kgiusti/qpid-proton,apache/qpid-proton,ChugR/qpid-proton