Fix t_seqstate build with Solaris compiler

The Solaris native compiler (as of version 5.9) outputs code for
static inline functions even if they are not used.  So the
k5buf_to_gss helper in gssapiP_generic.h causes t_seqstate to have a
dependency on libkrb5support.

ticket: 7872
Get getopt from unistd.h (not getopt.h) in tests

POSIX defines getopt to be declared in unistd.h, and HP-UX (as of
version 11.31) does not appear to have getopt.h.  In test programs
which currently include getopt.h and aren't currently built on
Windows, include unistd.h or just assume we will get it via k5-int.h.

ticket: 7894 (new)
target_version: 1.12.2
tags: pullup