Test suite code coverage loss with removal of application tests

[ghudson@MIT.EDU]

If the application tests are removed from the suite, the following
functions drop to 0% coverage or drop below 50% coverage:

  cvtaddr                            38% ->  0%
  decrypt_credencdata		     80% ->  0%
  encrypt_credencpart		     47% ->  0%
  extend_file_to                     70% -> 30%
  krb5_auth_con_genaddrs	     76% ->  0%
  krb5_auth_con_getkey		     60% ->  0%
  krb5_fwd_tgt_creds		     51% ->  0%
  krb5_get_cred_via_tkt              63% -> 45%
  krb5_get_credentials_core          72% -> 47%
  krb5_init_secure_context	    100% ->  0%
  krb5_kuserok			     22% ->  0%
  krb5_mk_1cred			     88% ->  0%
  krb5_mk_ncred			     51% ->  0%
  krb5_mk_ncred_basic		     78% ->  0%
  krb5_rd_cred			     54% ->  0%
  krb5_rd_cred_basic		     75% ->  0%
  krb5_rd_req_decrypt_tkt_part       90% -> 86%
  krb5_recvauth_version		    100% ->  0%
  krb5_verify_checksum		     80% ->  0%
  recvauth_common                    51% -> 49%

To a first approximation, we need standalone tests for ticket
forwarding and kuserok.  I will work on those before proceeding with
the unbundling plan, and also improve my comparisons a bit to see
where there is serious damage that doesn't happen to cross the 50% or
0% thresholds.

I used gcov to do these measurements.  I'll add some notes to the
debugging tips section of the wiki about how to use gcov on the krb5
tree.