dynamic_bloom: replace some divide (remainder) operations with shifts in locality mode, and other improvements

Summary:
This patch changes meaning of options.bloom_locality: 0 means disable cache line optimization and any positive number means use CACHE_LINE_SIZE as block size (the previous behavior is the block size will be CACHE_LINE_SIZE*options.bloom_locality). By doing it, the divide operations inside a block can be replaced by a shift.

Performance is improved:
https://reviews.facebook.net/P471

Also, improve the basic algorithm in two ways:
(1) make sure num of blocks is an odd number
(2) rotate bytes after every probe in locality mode. Since the divider is 2^n, unless doing it, we are never able to use all the bits.
Improvements of false positive: https://reviews.facebook.net/P459

Test Plan: make all check

Reviewers: ljin, haobo

Reviewed By: haobo

Subscribers: dhruba, yhchiang, igor, leveldb

Differential Revision: https://reviews.facebook.net/D18843