comms/gqrx: update 20140313 -> 2.3.1

• Set PORTEPOCH
• Update COMMENT and pkg-descr
• Add LICENSE_FILE
• Remove obsolete dependency
• Mantainer approved

PR: 193404
Submitted by: Kevin Zheng <kevinz5000@gmail.com>
Reviewed by: martymac (maintainer)
Approved by: mentors (implicit), martymac (maintainer)