Merge branch 'rename-packet-to-message' into libradsec-user-dispatch

Merge branch 'rename-packet-to-message' into libradsec-user-dispatch

Conflicts:
	lib/include/radsec/radsec.h

Original commit message (1e3a2613):

    Rename most 'package' to 'message'.

    RADIUS (RFC2865) is defined to be transported over UDP so the term
    "radius packet" makes a lot of sense. RADIUS/TCP (RFC6613) and
    RADIUS/TLS (RFC6614), a.k.a. RadSec, use stream transport protocols
    though. The term "message" doesn't imply any kind of transport -- a
    message can be sent using datagrams as well as in a stream.

    This (large) commit changes 'package' to 'message' where it makes
    sense. It does not touch the 'radius' subdirectory. It includes
    preprocessor directives (#define) to make the public interface
    compatible with previous releases of the library.