Windows: remove warnings afskfw.c

Windows: remove warnings afskfw.c

Sometimes warnings are errors and sometimes they are just warnings.
In this case, the krb5 error message functions were being passed
a krb5_context with the wrong level of indirection which resulted
in an actual error.  Other warnings were due to improper typing
and unnecessary casts.  Fix them all.

Change-Id: Ib2cefe94acca858dda9af92baaae3168c074bb2e
Reviewed-on: http://gerrit.openafs.org/5344
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>