abc initial commit

[jsorocil_gmail.com]

Summary

ABC is System for Sequential Logic Synthesis and Formal Verification.
It is a dependency for other parts of FPGA toolchain which will be added in other commits.

[jsorocil_gmail.com]

I'm not sure what type of BSD license is this:
https://github.com/berkeley-abc/abc/blob/master/copyright.txt
I have asked the author, but for now there is no reply.