Release leveldb 1.12

Non-functional changes only:
1) Add Kevin Regan to the AUTHORS file
2) Add standard license header to issues/issue178_test.cc
LevelDB 1.13

Fix issues 77, 87, 182, 190.

Additionally, fix the bug described in
https://groups.google.com/d/msg/leveldb/yL6h1mAOc20/vLU64RylIdMJ
where a large contiguous keyspace of deleted data was not getting
compacted.

Also fix a bug where options.max_open_files was not getting clamped
properly.
Revert "Remove read-driven compactions."

This reverts commit 939893f0daaefd3641f6758df4d3423b394b709f.

Conflicts:
	db/version_set.cc

This brings back the infrastructure for tracking files that see excessive reads.
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  LevelDB 1.13
  Release leveldb 1.12

Conflicts:
	AUTHORS
	Makefile
	db/corruption_test.cc
	db/db_impl.cc
	db/db_impl.h
	db/version_set.cc
	util/env_posix.cc