Don't include <errno.h>,

Don't include <errno.h>,
<sys/param.h>, <time.h>; not needed to establish interface.
(errno): Remove decl.
(HAVE_STRUCT_XTMP_UT_TYPE): Remove; no longer needed.
(UT_TYPE_EQ, UT_TYPE_NOT_DEFINED, UT_TYPE_BOOT_TIME,
UT_TYPE_USER_PROCESS, IS_USER_PROCESS): New macros.