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.

MFC after: 2 weeks
Sponsored by: Dell EMC Isilon