Added !SSPI to the features list of the HTTP digest tests, as SSPI
based builds now use the Windows SSPI messaging API rather than the
internal functions, and we can't control the random numbers that get
used as part of the digest.
(http://curl.haxx.se/bug/view.cgi?id=2535504) pointing out that realms with
quoted quotation marks in HTTP Digest headers didn't work. I've now added
test case 1095 that verifies my fix.