[BUG] 'fc -s' infinite loop

[Martijn Dekker <martijn@xxxxxxxx>]

On dash and on gwsh, the 'fc -s' command, that re-executes a command 
from the history, executes the command repeatedly in an infinite loop. 
It should execute it just once.

$ dash
$ echo foo
foo
$ fc -l
    1 echo foo
$ fc -s 1
echo foo
foo
echo foo
foo
echo foo
foo
echo foo
foo
echo foo
foo
echo foo
foo
[...]

Repeatable as of dash-0.5.7 (on 0.5.6.1 and early it's also broken but 
in a different way).

- M.