Removed psmisc from deps list (usually fuser is already installed and the package name for it varies)
Added "blif -unbuf" feature
Added "write_blif -blackbox"

based on code by Eddie Hung from
https://github.com/eddiehung/yosys/commit/1e481661cb4a4
Added "write_blif -undef" and support for special "-" true/false/undef type