[krbdev.mit.edu #2856] Need a function to clone krb5_context structs for thread safe apps

["Jeffrey Altman [Kermit Project]" via RT]

Sam Hartman via RT wrote:

> It's important to note that applications need not free an object with
> the same context used to acquire that object.  The only case where
> this is needed is if the application makes per-context configuration
> changes.

I disagree.  The claim has been made in response to ticket 2855 that 
thread safety is only ensured if no two threads make calls into the
library using the same context at the same time.  Therefore, there
must be one instance of the context for each thread.

If this is not the case, then the problem described in 2855 is in
fact a thread safety issue.