Syntax change for krb5.conf to use URL form

New syntax is `kdc = [(udp|tcp)://]<addr.of.kdc>[:<port>]`.
Expand socktype usage to protocol enumerator

The protocol enumerator retains all socktype definitions (preserving
compatibility) while allowing for new protocols to be defined.
Add HTTP transport for traffic

HTTP transport uses base64 encoding and POST requests to encapsulate
messages.  Configuration file syntax changed to:
`kdc = [(tcp|udp|http)://]<addr.of.kdc>[:<port>]`.
Enable kpasswd protocol to use HTTP for transport

Forces kpasswd to respect the transport protocol defined in krb5.conf
instead of ignoring it and choosing UDP.
Allow specification of page to POST to for HTTP

krb5.conf syntax is now:
`kdc = [(tcp|udp|http)://]<addr.of.kdc>[:<port>][/<page>]`
Add HTTPS transport for traffic

krb5.conf syntax is now:
`kdc = [(tcp|udp|http|https)]://<addr.of.kdc>[:<port>][/<page>]`