Initial checkin of Mac OS X ipc support.

Initial checkin of Mac OS X ipc support.
Also moved "set application name" functionality to kim_library_
because most applications do not need to call it and their name
doesn't usually change over time or per thread By putting it
in a global setting apps that do need to call it only have to
call it once instead of every time they want to authenticate.

ticket: 6055

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20757 dc483132-0cff-0310-8789-dd5450dbe970