Debugging API for krb5

[Sam Hartman]

It seems like you want the debug_message function to take a mask or
level at which the message you are debugging is appropriate.  Your
current proposal does not do this.

Also, I'm not clear that 32-bits is sufficient.

I propose that we not worry about the API for setting the debugging
mask at this time, but just worry about the API for generating
debugging messages.

I do understand that KFW will need some internal API for turning on
debugging, but that can remain internal and be revised in the future.