shill: cellular: Fix ModemManager header inclusion.

The upstream ModemManager now disallows including ModemManager-enums.h
and ModemManager-names.h directly. This CL fixes the ModemManager header
inclusion as follows:
- Use pkg-config in Makefile to specify CFLAGS for including
  ModemManager headers
- Include ModemManager.h instead of ModemManager-enums.h and
  ModemManager-names.h
- Move ModemManager1 related code from modem_manager.cc to a new
  modem_manager_1.cc in order to avoid including both mm-modem.h and
  ModemManager.h

BUG=chromium-os:35075
TEST=Build and run unit tests.

Change-Id: Ice180f673562c8b71500e2bec861de80f45148fc
Reviewed-on: https://gerrit.chromium.org/gerrit/34734
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
diff --git a/cellular_capability_universal_unittest.cc b/cellular_capability_universal_unittest.cc
index 5f0cc2e..f89a91e 100644
--- a/cellular_capability_universal_unittest.cc
+++ b/cellular_capability_universal_unittest.cc
@@ -12,7 +12,7 @@
 #include <chromeos/dbus/service_constants.h>
 #include <gtest/gtest.h>
 #include <mobile_provider.h>
-#include <ModemManager/ModemManager-names.h>
+#include <ModemManager/ModemManager.h>
 
 #include "shill/cellular.h"
 #include "shill/cellular_service.h"