Throughout the jdwp library coding, the header size of a jdwp header is used sometimes literally, sometimes via define. This should be cleaned up.

Furthermore, there exist 2 little bugs in src/jdk.jdwp.agent/share/native/libjdwp/inStream.c:
    inStream_init should initialize stream->left with the packet size without the JDWP Header size.
    inStream_endOfInput is implemented completely wrong but it seems that the function is not used/needed at all.