There were three RFCs listed in list of "RFCs we implement" but missing
in the ARM.
Command to compare lists in the two documents:
diff <(grep -o '^ RFC[0-9]\+' doc/misc/rfc-compliance | sed -e 's/[^0-9]//g' | sort -n) <(grep '^:rfc:`' doc/arm/general.rst | sed -e 's/^.*`\([0-9]*\)`.*$/\1/' | sort -n)
6908b46011