Succinct ESA output

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ESA can be represented by a BP representation. 
An internal node information can be replaced by a rank operation on BP. 

First, build a permutated hight array from SA directly, which is 2n bits of 
space, and then use this to compute BP. Since currently nodes are enumerated 
in post order, we need to convert this into the BP; that is pre-order

Original issue reported on code.google.com by Daisuke.Okanohara on 26 May 2010 at 1:39