Move OTP sockets to KDC_RUN_DIR

Some system configurations expect Unix-domain sockets to live under
/run or /var/run, and not other parts of /var where persistent
application state lives.  Define a new directory KDC_RUN_DIR using
$runstatedir (new in autoconf 2.70, so fall back to $localstatedir/run
if it's not set) and use that for the default socket path.

[ghudson@mit.edu: commit message, otp.rst formatting fix]

ticket: 7859 (new)
Portable transport enumerator
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
HTTPS transport (Microsoft KKDCPP implementation)
Be more exacting about the reply content-length
Remove a check on the kpasswd server's address

This test breaks when we're sending password changes over HTTP, and most
likely under NAT, too.
Track the realm name for MS-KKDCP

Always pass a realm name to set_conn_state_msg_length(), to ensure that
we include the not-actually-optional target-domain field if we're using
MS-KKDCP.
Don't try to zero the byte after the buffer
Add http_anchors and http_revoke settings

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

Add an http_hostname option, though for now it only specifies alternate
CN values that we'd accept in the server's certificate's subject name
field.
Support dnsName subjectAltName hostname matching

Parse subjectAltName extensions when checking for a hostname match,
which also requires that we accept certificates without subject names.
Mention that MS-KKDCP also encrypts names
Don't fall for zero-byte-in-the-CN
Differentiate HTTPS and TCP trace messages
Add certificates for a testing MS-KKDCP proxy
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.
Learn to start and stop the test MS-KKDCP proxy