emulators/qemu-devel: Update version 4.2.0=>5.1.0.20200909

• Move to SNAPSHOT versions of qemu
• Remove i386 support temporarily as build is failing on i386
• Change MASTER_SITES to GITHUB
• Mark IGNORE for 11.X as it cannot build Position Independent Code on 11
• OPTIONIZE NCURSES for support of both base and ports [1]
• Add OPTIONS CAPSTONE and use CAPSTONE from ports
• Remove PCAP related patches as was unable to create PANIC while using TSO
• Fixes for the RISC-V PLIC that are required to boot FreeBSD/riscv64 HEAD after r362977

PR: 245997 [1]
Submitted by: lab+bsd@thinkum.space [1]
Reported by: lwhsu jhb