crypto: Use our strcasecmp in kernel

crypto: Use our strcasecmp in kernel

A few pieces of heimdal we use in the kernel call strcasecmp
(hcrypto/evp.c, krb5/crypto.c). The strcasecmp function does not exist
in all kernels (specifically, it does not exist in at least Linux 2.4,
2.6.9, and probably not on Solaris pre-10). Since we have our own copy
of strcasecmp (called afs_strcasecmp), just use that for now.

Ideally we would have some kind of configure test for detecting the
presence of the function in the kernel, and use the roken
implementation when we don't. We currently have the framework for
neither of those in place at the moment, though, so just get by with
this for now.

Change-Id: Ia96b17596da6cb168c80c92486fa049c05205da4
Reviewed-on: http://gerrit.openafs.org/7881
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementix.org>