Release LevelDB 1.17

- Cleanup: delete unused IntSetToString

  It was added in http://cr/19491949 (and was referenced at the time).
  The last reference was removed in http://cr/19507363.

  This fixes warning/error with pre-release crosstoolv18:
    'std::string leveldb::{anonymous}::IntSetToString(const std::set<long unsigned int>&)' defined but not used [-Werror=unused-function]

- Added arm64 and and armv7s to IOS build as suggested on leveldb mailing list.

- Changed local variable type from int to size_t

  This eliminates compiler warning/error and resolves
  https://code.google.com/p/leveldb/issues/detail?id=140
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Release LevelDB 1.17

Conflicts:
	Makefile
Concurrency improvements.

Described here:
http://hackingdistributed.com/2014/06/18/hyperleveldb-improvements/