LU-6490 gss: 3.1x kernels adjustments for gssapi code

LU-6490 gss: 3.1x kernels adjustments for gssapi code

There are a number of changes in 3.1x kernels concerning the GSSAPI:
- libgssapi and libgssglue do not exist anymore, so call krb5
  primitives directly, and remove associated config checks;
- struct cred has no tgcred member anymore, so use cred directly;
- struct key_type instantiate and update function prototypes
  have changed;
- add new config checks on struct cred and struct key_type;
- u_int is BSD specific, so it is replaced with unsigned int.

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: I3b13c2afcb4b800bdcffb3b8713048f8e39f6866
Reviewed-on: http://review.whamcloud.com/15342
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>