bug#70532: sort: Mention counting fields from the end

[Dan Jacobson]

>>>>> "PB" == Pádraig Brady <P@draigBrady.com> writes:
PB> All good suggestions. I'll at least add an example along the lines of:

PB>   awk '{print $NF, $0}' | sort -k1,1 | cut -f2- -d' '

OK, also say what it's doing. Not everybody knows awk.

Also join(1) needs a tip added. Users might want to join on
e.g., the second to last field on a variable-number-of-fields file.