Always stat profile files after reopening them

Some applications write a profile file and then immediately use it via
a krb5_context.  If we have a cached copy of the profile we wrote,
make sure to update it by forcing a stat when we reuse an existing
prf_data_t object.

[ghudson@mit.edu: commit message]

ticket: 7884
Don't check kpasswd reply address

Don't check the address of the kpasswd server when parsing the reply
we received from it.  If the server's address was modified by a proxy
or other network element, the user will be incorrectly warned that the
password change failed when it succeeded.  The check is unnecessary as
the kpasswd protocol is not subject to a reflection attack.

[ghudson@mit.edu: edit commit message]

ticket: 7886 (new)
Make use of strtoul() unconditional in locate_kdc

When parsing port numbers, we previously attempted to conditionalize use
of strtoul() on whether or not it was available, falling back to atoi()
instead, but we did so in a way that would always fall back to using
atoi().  We also call strtoul() from elsewhere without that condition,
so we don't gain anything by trying to be careful about it here.
Use portable transport enumerator for k5_sendto

In k5_sendto and k5_locate_server, replace "socktype" parameters with
a new enumerator k5_transport, so that we can add new transports which
are not in the socket type namespace.

[ghudson@mit.edu: renamed type to k5_transport; clarified commit
message]
[kaduk@mit.edu: use 'transport' for the name of variables of type k5_transport]
[nalin@redhat.com: update the test program]
Build support for HTTPS transport
Remaining cm read/write mutator functions
Add ASN.1 codec for KKDCP's KDC-PROXY-MESSAGE
Dispatch-style protocol switching for transport

Switch to using per-transport-type functions when a socket that we're
using to communicate with a server becomes readable or writable, and add
them as pointers to the connection state.

[nalin@redhat.com: replace macros with typedefs]
[nalin@redhat.com: compare transports with TCP_OR_UDP rather than with 0]
[nalin@redhat.com: reorder conditional bits to always check for UDP first]
HTTPS transport (Microsoft KKDCPP implementation)

[nalin@redhat.com: use cleanup labels, make sure we always send the
 realm name, keep a copy of the URI on-hand, move most of the
 conditionally-compiled sections into their own conditionally-built
 functions, break out HTTPS request formatting into a helper function,
 update comments to mention specific versions of the MS-KKDCP spec,
 differentiate TCP and HTTP trace messages]
Add http_anchors, _revoke, and _hostname settings

Add http_anchors, http_revoke, http_hostname and
http_require_crl_checking settings, mimicking both the locations and
effects of their similarly-named PKINIT counterparts, but affecting
HTTPS connections to KDC proxy servers.

The hostname checking currently assumes UTF-8 everywhere.
Add a simple KDC proxy test server

This proxy server uses python-paste to run the kdcproxy from
https://pypi.python.org/pypi/kdcproxy.  It should be used along
with the proxy.pem certificate in ../tests/dejagnu/proxy-certs.
Add tests for MS-KKDCP client support

Exercise the MS-KKDCP client support using the test proxy server.