Hack too ugly? Just remove it.
Excise interruptor in sindex acquisition methods.

It's not needed with the alt cache.
More excising of interrupters in sindex methods.
Remove several RSIs that were just questions.
Fixes drop_sindex as per RSIs.
Fix drop_all_sindexes.

The changes are aprroximately identical to those made in drop_sindexes.
Similar enough that I moved a lot of the logic in to a common function.
real_superblock_t now takes an rvalue ref.

Previously it would call the swap method on the buf_lock it was passed.
No need to swap when you have move semantics.
Add a comment explaining an RSI.
Addresses several RSIs.

We release the superblock a little bit earlier than before in
store_t::store_t.

Comment about how txn will be removed in rdb_read_visitor_t.

Remove some bs with get_event_log().
sindex_block doesn't exist when SLICE_ALT == 1

Removes an RSI to this effect.
Removing several RSIs.
Make an enum expired_t to pass to apply_keyvalue_change.

I got the inspiration from this commit from an RSI by sam. Which is
where I get the inspiration for all of my commits these days.
Fixes a bug with alt_buf_write_t lifetime.

I also checked all of the alt_buf_write_t and made sure the lifetime is
safe.
Fix a compile error.
Relocate an RSI.
Fixes several RSIs.
Update an RSI.
Merge branch 'sam_alt' into sam_jd_alt
Moved access_ref_count_ decrement to alt_buf_write_t destructor.
Removed untrue comment in set_sindexes about releasing sindex_block.