ueventd: Break devices.cpp into discrete classes

devices.cpp handles too many things for creating one class.  This
change breaks it up into various files and classes.

* Parsing is moved to ueventd_parser.cpp
* Reading from the uevent socket and Cold booting is moved to a
  UeventListener class, in uevent_listener.cpp
* Firmware handling is moved to firmware_handler.cpp
* The remaining contents form a DeviceHandler class within devices.cpp

Bug: 33785894

Test: boot bullhead x40, observe no major differences in /dev and /sys
Test: boot sailfish x40, observe no major differences in /dev and /sys
Test: init unit tests

Change-Id: I846a2e5995fbb344c7a8e349065c18a934fa6aba
diff --git a/init/uevent.h b/init/uevent.h
new file mode 100644
index 0000000..1095665
--- /dev/null
+++ b/init/uevent.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _INIT_UEVENT_H
+#define _INIT_UEVENT_H
+
+#include <string>
+
+struct Uevent {
+    std::string action;
+    std::string path;
+    std::string subsystem;
+    std::string firmware;
+    std::string partition_name;
+    std::string device_name;
+    int partition_num;
+    int major;
+    int minor;
+};
+
+#endif