New bzip dependency?

[gadomski]

As I was re-building PDAL on a clean system today, I came across:

/home/gadomski/Code/PDAL/boost/libs/iostreams/src/bzip2.cpp:20:56: fatal error: bzlib.h: No such file or directory

Seems like 85c1913 may have introduced bzip as a dependency (called libbz2-dev for apt-get). I just wanted to confirm that was the case before I add a note to the docs.