Off-by-one in open ended csvcut range

If the column range for csvcut is open ended, the last column is missing:

$ echo "a,b,c" | csvcut -c1-
a,b

but with this patch it works as expected:

$ echo "a,b,c" | csvcut -c1-
a,b,c

This mimics the behaviour for cut:

$ echo "a,b,c" | cut -d"," -f1-
a,b,c