Add MIPS support and other fixes

PR: 215938

• Main PR that merge all

Submitted by: luca.pizzamiglio@gmail.com (maintainer)

PR: 215783

• Add MIPS support

Submitted by: jhb
Sponsored by: DARPA / AFRL

PR: 215868

• Fix build on powerpc architecture

Reported by: Mark Millard

PR: 212607

• Add a workaround to mitigate gdb hangs under some circumstances

with multi-threaded applications
(thanks to misc-freebsd-bugzilla@talk2dom.com)
Reported by: tijl

PR: 215578

• Fix build by removing option to use system readline

Reported by: rozhuk.im@gmail.com