histedit: Fix "fc -3" breakage on glibc

Before:
	$ echo a
	a
	$ echo b
	b
	$ fc -2 -1
	src/dash: 3: fc: unknown option: -2
	$ fc -- -2 -1
	16
	,p
	echo b
	fc -2 -1
After:
	$ echo a
	a
	$ echo b
	b
	$ fc -2 -1
	6
	,p
	echo a
	echo b

Reported-by: Harald van Dijk <harald@gigawatt.nl>
Reported-in: https://marc.info/?l=dash&m=154707728009743&w=2
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>