fragment6 now preserves custom values in the nh field.
fragment6 now preserves custom values in the nh field.

fragment6 was not preserving the value of the nh (next header) field
when explicitly set. With something like
`IPv6()/IPv6ExtHdrFragment()/UDP()/'payload'` nh was preserved, but
with `IPv6()/IPv6ExtHdrFragment(nh=254)/'payload'` it was not. In the
latter case, the resulting fragments had a value of 59 (no next
header) in nh.

mytliulei/Scapy,mytliulei/Scapy