There is a memory leak here, if a thread has registered some per-thread data

There is a memory leak here, if a thread has registered some per-thread data
when we delete the key.  Fixing it will require walking through the per-thread
data of every thread and freeing the objects... and watching for deadlocks in
the case where a thread is exiting at the same time.

* threads.c (k5_key_delete) [pthread case]: Reset flags and destructor function
pointer to unset state.
(krb5int_thread_support_init, krb5int_thread_support_fini): If
SHOW_INITFINI_FUNCS is defined, print some tracing messages.

ticket: 2916
status: open

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@17092 dc483132-0cff-0310-8789-dd5450dbe970