libpcap: import homebrew/dupes into core.

Formula/libpcap.rb

@@ -0,0 +1,27 @@
+class Libpcap < Formula
+  desc "Portable library for network traffic capture"
+  homepage "http://www.tcpdump.org/"
+  url "http://www.tcpdump.org/release/libpcap-1.8.1.tar.gz"
+  sha256 "673dbc69fdc3f5a86fb5759ab19899039a8e5e6c631749e48dcd9c6f0c83541e"
+  head "git://bpf.tcpdump.org/libpcap"
+
+  bottle do
+    cellar :any
+    sha256 "95a69600f13a8fae57c9d96f436a5161a0eb30f7c121dad25518039381663661" => :sierra
+    sha256 "a68ac5c1c4b570fdf288c0049524c232d9122ef2c6eeae95e4f7a87f9fd6f4a4" => :el_capitan
+    sha256 "e7d313172264c39a22038ac0c6fa67e1ce796406a761511b6a854a4e5a3f05dc" => :yosemite
+  end
+
+  keg_only :provided_by_osx
+
+  def install
+    system "./configure", "--prefix=#{prefix}",
+                          "--enable-ipv6",
+                          "--disable-universal"
+    system "make", "install"
+  end
+
+  test do
+    assert_match /lpcap/, shell_output("#{bin}/pcap-config --libs")
+  end
+end