Unbreak on 11.x+ by removing reference to unused header file.

Turns out there was a much simpler solution for this build failure. By simply removing reference to "pcap-int.h" (which was not used at all) now this port builds on 10.x, 11.x and 12x just fine.

Removed reference to unnecessary header files to unbreak on 11.x and 12.x

Addressed in D8897

In D9091#187890, @bapt wrote:

Why adding a new one instead of upgrading the old one?

Update net/radvd to 2.15

Fixed as per @bapt recommendations

In D8474#176540, @bapt wrote:

have you analysed what are the difference between former version and newer?
sounds like the moved the tag meaning the package would probably be different meaning a bump of the port revision might be needed

In D8472#176545, @bapt wrote:

You are missing a MOVED entry

Update MOVED file

In D7197#149607, @olgeni wrote:

textproc/erlang-p1xml should probably be replaced by https://github.com/processone/fast_xml

Update as per mat's suggestions

In D8471#176164, @mat wrote:

Is this just the removal of the port, or should it be a move ?