An extremely memory-efficient hash_map implementation. 2 bits/entry overhead!
The Google SparseHash project contains several hash-map implementations in use
at Google, with different performance characteristics, including an
implementation that optimizes for space and one that optimizes for speed.
WWW: http://goog-sparsehash.sf.net
PR: ports/82696
Submitted by: Vasil Dimov <vd@datamax.bg>
