Added parsing of SNF_FLAGS, packet injection, snf_findalldevs for SNF API

Bug Fixes so --with-pcap=snf builds properly
Added back in EBUSY as it can be returned in SNFv3 by snf_ring_recv().
using the PACKET_COUNT_IS_UNLIMITED() macro
using the PACKET_COUNT_IS_UNLIMITED() macro
Introduce bpf_filter1 function

Function takes additional argument which is a pointer to bpf_aux_data
structure. This newly introduced struct holds auxiliary data provided by caller
to specify additional data needed to implement some BPF extensions while
executing filter in userspace.

bpf_filter1 currently implements support for two BPF extesions, namely
vlan_tci and vlan_pr.
Use BPF extensions in compiled filters

libpcap will generate BPF filter code which uses BPF extensions if target
platform supports them. Currently supported BPF extensions are vlan_tci and
vlan_pr.

Also to properly handle such filters when filtering in userspace libpcap now
employs bpf_filter1.
Merge pull request #391 from msekletar/vlan-bpf

[RFC] Fix vlan filtering on Linux
More descriptive name for bpf_filter1().

Call it bpf_filter_with_aux_data(), to better indicate what it does.

Also expand some comments and clean up white space a bit.
Get rid of unused variable.

Also clean up white space a bit.
Move the socket ops out of gencode.c.

Instead, do it in pcap-linux.c, and have it set a flag in the pcap_t
structure to indicate to the code in gencode.c that it needs to generate
special VLAN-handling code.
<linux/filter.h> needs <linux/types.h>, and it's not automatically included.

This fixes build errors on, for example, a Red Hat system with a 2.6.9
kernel.
Not all systems have <stdint.h>

Don't include it, and use u_intXX_t, which we arrange to be defined,
rather than uintXX_t.
There's no pcap_t argument to code generator routines.

Use the global bpf_pcap instead.
Use u_short rather than u_int16_t; that's what we do elsewhere.

u_int16_t is not guaranteed to be defined when this is included by
applications (for example, tcpdump).
fix compiling with SO_BPF_EXTENSIONS

Add a missing parenthesis and use socklen_t for the getsockopt()
argument to address a pointer type warning.
Fix --enable-dbus to work on platforms other than OS X.

Addresses GitHub issue #385.
Merge pull request #375 from myri/master

Added parsing of SNF_FLAGS, packet injection, snf_findalldevs for SNF API