Handle value -> NULL gracefully like NetBSD does

Sponsored-by: EMC Isilon
MFC r254095:
  gpt_entries is used as limit for the number of partition entries in
  the GEOM_PART. Instead of just using number of entries from the GPT
  header, calculate this limit based on the reserved space between
  GPT header and first available LBA.
MFC r253494:
id_t is 64bit, provide the compat32 wrapper for clock_getcpuclockid2(2).

Reminded by:	Petr Salinger <Petr.Salinger@seznam.cz>
Regenerate.
Revert r254626 to fix the build.
Merge branch 'stable/9' of github.com:yaneurabeya/freebsd into stable/9
Merge remote-tracking branch 'upstream/stable/9' into stable/9