As with sk_*, this. This doesn't fix the function pointer casts. Those
will be done in a follow-up change. Also add a test for lh_*_doall so we
cover both function pointer shapes.

Update-Note: This reworks how LHASH_OF(T) is implemented and also only
pulls in the definitions where used, but LHASH_OF(T) is never used
externally, so I wouldn't expect this to affect things.

Change-Id: I7970ce8c41b8589d6672b71dd03658d0e3bd89a7
Reviewed-on: https://boringssl-review.googlesource.com/c/32119
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>