Move kprop error explanation into Troubleshooting

The plan is to make Troubleshooting section of the documentation a
one-stop-shop place for all error diagnostics, explanations and possible
solutions.  The relocation of kprop error messages descriptions is part of
this consolidation effort.
Fix typo that broke 'make clean'

Missing $
Move kdc log routines into a separate file

Their previous location - kdc_util.c - seems to be overloaded with
various helper functions. No code changes.
Test for verto_set_flags in system libverto

libkrad relies on verto_set_flags, which was added to libverto in
release 0.2.4.  Make sure the system libverto has this function before
choosing it over the built-in version.

ticket: 7808 (new)
target_version: 1.12.1
tags: pullup
Set an error message when keyring get_princ fails

When attempting to use a keyring cache that doesn't exist, set an error
message when we fail to read a principal name, as we do when we return
the same error code when using a file ccache.

[ghudson: removed unnecessary check for d->name nullity.]

ticket: 7809
target_version: 1.12.1
tags: pullup
Use an extended com_err hook in klist

Add an adapted version of extended_com_err_fn from kinit to klist and
use it.  In do_ccache(), rely on the ccache type to set a reasonable
message if krb5_cc_set_flags() or krb5_cc_get_principal() fails due to
a nonexistent or unreadable ccache, and don't confuse the user with
the name of the ccache operation that failed.

ticket: 7809
Avoid keyctl purge in keyring ccache tests

keyctl purge was added in keyutils 1.5 (released in March 2011).  Use
keyctl unlink to clean up keys instead, as it is more universal.

ticket: 7810
target_version: 1.12.1
tags: pullup
Require built-in verto for make depend

A tree configured to use the system libverto will be missing
$(VERTO_DEPS) in dependencies, so disallow make depend.
make depend
Simplify libkadm5 client realm initialization

The "realm" variable in init_any is used only to fill in the realm of
the service principal in gic_iter().  The service principal realm
should always be the realm we looked up config parameters for, so we
can supply that realm to get_init_creds() unconditionally and
eliminate the case where we use the client principal realm.

Also get rid of an outdated comment and an #if 0 block we will never
need again, and use SNPRINTF_OVERFLOW to check the snprintf result.
Allow realm in kadm5_init service names

Previously, if you passed a service name with a realm part to a
kadm5_init function, you would get a KRB5_PARSE_MALFORMED error
because the code would internally append its own '@realm' suffix
before parsing the name.  Fix this as follows:

Change gic_iter so instead of producing a full service name, it
produces a krb5_principal which is taken from the cred it acquires.
Pass the client and full service name around as principals, rather
than strings, and use the gss_nt_krb5_principal name type to import
them in setup_gss().  Don't append a realm to the input service name;
instead, pass the input service name directly to the gic functions
(which do not need a realm in the service name and will ignore the
realm if one is present).  For the INIT_CREDS case, parse the input
service name with KRB5_PRINCIPAL_PARSE_IGNORE_REALM and then set the
realm.

ticket: 7800
Fix uninitialized warning in client_init.c

ticket: 7800