Build instructions for Ubuntu 16.04 about heavydb

[andrewseidl]

The very last batch of commands in the dependency build section builds and installs bison++. We don't have it in the list of packages installed with apt because it interacts with some of the build deps required for Thrift.

It's fine to install from apt after Thrift is built, you just might be forced to uninstall that package if you ever have to rebuild Thrift (it's a bug in how the build-deps and package conflicts are set up in the repositories, not an actual issue with Thrift/flex/bison++).

[mcowart123]

I could not get make to run successfully (it failed looking for flex) until I manually did an apt install of bison++. This was after running all the dependency builds. I put all the dependency commands into a script I ran as root (altering it to remove any sudo). I'm not going to say it's impossible there were any errors, but I didn't notice any in the output.