bug#55212: GNU Linux "sort -g" can hang indefinitely when run on standard input if NaNs are involved

[Giulio Genovese]

As explained here
<https://unix.stackexchange.com/questions/700863/gnu-linux-sort-g-can-hang-indefinitely-when-run-on-standard-input-on-ubuntu>,
when running "sort -g" from standard input, if NaNs are involved, this can
cause "sort -g" to hang indefinitely while consuming 100% of the CPU. This
seems to be system dependent. I cannot reproduce the bug on a RHEL7
machine. However, multiple users seem to be able to reproduce the bug. The
following command can provoke the bug:

yes nan | head -n128095 | timeout 5 sort -g