No functional differences.
- use the div64() macro to wrap 64 bit divisions
(which almost always are 64 / 32 bits) so they are easier
to handle with compilers or OS that do not have native
support for 64bit divisions;
- use a local variable for p_numbytes even if not strictly
necessary on HEAD, as it reduces diffs with FreeBSD7
- in dummynet_send() check that a tag is present before
dereferencing the pointer.
- add a couple of blank lines for readability near the end of a function
MFC after: 3 days