From 9.0 to 9.1
  - accelerated BWT calculation
  - fixed a bug in the construction of int_wavelet_tree
  - added new lcp construction method (goPHI)

From 0.8 to 9.0
  - added int_wavelet_tree
  - added semi-external construction of csts
  - added new lcp construction methods (go, go2)  
