Improved the sindex_wait() polling nap logic. Minor cleanup of the sindex not ready error handling.
Fixed a bug in the sindex status retrieval. It only considered the first shard multiple times, rather than considering all shards.
adding --hard option to rethinkdb-import
adding --hard option to rethinkdb-restore
changing default cache size to be smaller, but adding a minimum size of 100 MB, extra warnings about low cache size or low available memory
changing --hard to --hard-durability in import/restore
removed crazy logic
changing buffer cache soft throttling to scale based on cache size
moving transaction throttling limit changing logic into the throttler
changing disk-backed queues to have a base cache size of 2 MB
code review cleanup
Merge branch 'v1.12.x' of github.com:rethinkdb/rethinkdb into v1.12.x
draft release notes for 1.12.1
Improve build-rpm.sh script
Unset DESTDIR in pkg.sh and edit v8 CXXFLAGS
Remove a reference to the old support.mk
Always use --host flag when compiling libunwind
Use the correct architecture flag when building RPM
Fix v8 build error on centos
Merge branch atnnn/2183 into next

Closes #2183
Closes #2176
Closes #1491

Review 1380 by @mlucy