Use 14 instead of 9 for unkeyed SHA-1 checksum

Use 14 instead of 9 for unkeyed SHA-1 checksum

Although MIT krb5 had been using the value 9 for unkeyed SHA-1 since
its 1.0 release in 1996, RFC 3961 instead assigned this value to
rsa-md5-des3 (likely never used), and assigned the values 10 and 14 to
SHA-1.  Heimdal and Microsoft use the value 14.  Unkeyed SHA-1 almost
never appears on the wire, but has been seen in PKINIT asChecksum
fields in replies from Windows KDCs (despite the field being specified
as a keyed checksum).

Define a new symbol CKSUMTYPE_SHA1 with the value 14, and use it where
we currently use CKSUMTYPE_NIST_SHA.  Continue to allow the value 9
for ABI compatibility.  Remove the pkinit_clnt.c workaround as the
value 14 will now work without adjustment.

ticket: 9040 (new)