fix(upower): add missing include for libc++

In file included from src/modules/upower/upower.cpp:1:
include/modules/upower/upower.hpp:25:16: error: no template named 'unordered_map' in namespace 'std'
  typedef std::unordered_map<std::string, UpDevice *> Devices;
          ~~~~~^
In file included from src/modules/upower/upower_tooltip.cpp:1:
include/modules/upower/upower_tooltip.hpp:13:16: error: no template named 'unordered_map' in namespace 'std'
  typedef std::unordered_map<std::string, UpDevice*> Devices;
          ~~~~~^

include/modules/upower/upower.hpp

@@ -5,6 +5,7 @@
 #include <iostream>
 #include <map>
 #include <string>
+#include <unordered_map>
 
 #include "ALabel.hpp"
 #include "glibconfig.h"

include/modules/upower/upower_tooltip.hpp

@@ -2,6 +2,8 @@
 
 #include <libupower-glib/upower.h>
 
+#include <unordered_map>
+
 #include "gtkmm/box.h"
 #include "gtkmm/label.h"
 #include "gtkmm/window.h"