Add dirty hack to build on new versions of libpng.
Add support for radiotap packets.
Commit hack to make radiotap sniffing work.
Better fix for radiotap.
Check for lack of adjunct in non-X after parsing options.
Merge branch 'master' of github.com:gamma9mu/driftnet
Merge branch 'master' of git://github.com/gamma9mu/driftnet
Change header removal handling

The original code assumes that headers are fixed sizes based on the datalink
type.  This is false, and the biggest example of a datalink type that is
variable length is radiotap.  I originally hacked this up by adding special
checks for radiotap and handling it separately, but this depended on the pc
pointer being globally available.  Instead, we only store the datalink type and
use this information to decide the length on every packet (there doesn't seem
to be a way to get past having datalink as a global variable since
process_packet is a callback).  This way we can support radiotap and any other
variable length headers in the future.
Update to work with modern versions of libpng.

Per http://libpng.sourceforge.net/ANNOUNCE-1.4.0.txt, png_set_gray_1_2_4_to_8() was renamed.
Fix typo: add library flags from pkg-config to LDLIBS, not cflags
Merge https://github.com/bldewolf/driftnet
Merge https://github.com/cfinucane/driftnet