fix typo
fix typo
prune whitespace
conditional compile support for snappy

This adds CMake support for conditionally compiling snappy support for blosc.
The FindSnappy script was taken from Hypertable and is GPL -- can reimplement
if needed. Should still be able to copy and paste sources, since HAVE_SNAPPY is
only defined via config.h, but will need an empty config.h... Not sure how to
solve that one yet.
only run snappy benchmark if lib was compiled with snappy support