#73 repair.sh swaps sequences in the output fastqs

[Ryan Zhu]

repair.sh is buggy when the input fastqs contain "2:N" in the header. The problem is seen in v39.15.
For example, when both in1 and in2 fastqs have "2:N", the output sequences will be swapped. When input fastqs are in the order of "2:N" and "1:N", the output sequences will be swapped to the order of "1:N" and "2:N".
The same problem was independently reported by another user here: https://www.biostars.org/p/9555618/