We want to use a particular version of boost random for our random number generators
so that our random numbers are deterministic given a particular initial seed.
This way, we can distribute configuration files with particular seed values and 
know that everyone will generate the same images from them.  

To this end, we have copied the random number parts of boost version 1.48.0.
We had to copy a few extra files as well in order to make sure this is compatible
with native boost distributions.  We have tested that this works when the 
native boost is 1.35 through 1.50, but if yours is older or newer than that,
there's a possibility that it won't work.

There are some includes from the main boost distro: <boost/...>.  These are guarded
with #ifdef USE_BOOST, which by default is not defined, so they are not used.
However, most of these files involve boost workarounds for various compiler issues,
so if you have trouble compiling this and have a local boost installation, you
can compile with `scons USE_BOOST=true` to enable this.