databases/libnvpair: New major version (so.1 => so.3)

The changes since version 1.0.2 were significant enough to warrant
a major library version bump. However, libnvpair.so.2 exists in
FreeBSD base, so the port version builds libnvpair.so.3 instead.

With one exception, all of the Solaris/Illumos types have been
replaced with BSD equivalents, including boolean_t. This changes
several prototypes, and also allows for the type compatibility header
to be removed. The one type that remains is hrtime_t (equivalent to
int64_t).

Internally, the regression tests for print_json (functionality that
does not exist in FreeBSD base, at least on F9) have been added from
Illumos regression tests and both DragonFly and FreeBSD pass.