MFC r313404:

Improve libnetbsd compatibility with NetBSD

This change is being made to diff reduce/reduce duplication in
contrib/netbsd-tests and to facilitate further porting of software from
NetBSD

Add the following headers:
- sys/event.h:
-- sys/types.h is required for kqueue on FreeBSD, but not NetBSD.
- sys/types.h:
-- NBBY is defined in sys/param.h on FreeBSD, not sys/types.h like on NetBSD.
Pull in sys/param.h to have parity with NetBSD.
- sys/wait.h:
-- Define wrusage as __wrusage for parity with NetBSD typedef.
- glob.h
-- Define __gl_stat_t as "struct stat" for parity with NetBSD typedef.
- pthread.h:
-- Pull in pthread_np.h for _np functions defined separately on FreeBSD.

Improve compatibility with NetBSD in the following headers:

- sha1.h:
-- define SHA1_CTX as SHA_CTX
-- define SHA1Final as SHA1_Final
- sha2.h:
-- #include sha384 to pick up all of the SHA 384 bit macros and definitions.
- util.h:
-- Add sys/types.h to util.h to pollute the header for types used in
flags_to_string and string_to_flags (u_long) as NetBSD doesn't require them
for the functions.