shill: Add IPAddress class

Add class that holds IP Addresses.  Routing will need these.
Move address family constants out of IPConfig to this new class.

BUG=chromium-os:17277
TEST=New unittest

Change-Id: I69d9c4d551061de890ed6919462597a15ae51857
Reviewed-on: http://gerrit.chromium.org/gerrit/4180
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
diff --git a/dhcp_config.cc b/dhcp_config.cc
index 0675a10..5a4a307 100644
--- a/dhcp_config.cc
+++ b/dhcp_config.cc
@@ -14,6 +14,7 @@
 #include "shill/dhcpcd_proxy.h"
 #include "shill/dhcp_provider.h"
 #include "shill/glib.h"
+#include "shill/ip_address.h"
 
 using std::string;
 using std::vector;
@@ -192,7 +193,7 @@
                                     IPConfig::Properties *properties) {
   VLOG(2) << __func__;
   properties->method = flimflam::kTypeDHCP;
-  properties->address_family = IPConfig::kAddressFamilyIPv4;
+  properties->address_family = IPAddress::kAddressFamilyIPv4;
   for (Configuration::const_iterator it = configuration.begin();
        it != configuration.end(); ++it) {
     const string &key = it->first;