Pull in mbedmicro/mbed

Pull in mbedmicro/mbed.  Make the following changes in addition:
- Ignore unused directories in mbed
- Add stub mbed-drivers/mbed.h for backwards compatibility
- Remove targets.json and instead use mbed's version

.mbedignore

@@ -0,0 +1,4 @@
+mbed/docs/*
+mbed/libraries/*
+mbed/travis/*
+mbed/workspace_tools/*

hal_temp/mbed-drivers/mbed.h

@@ -0,0 +1,21 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * 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 MBED_STUB_H
+#define MBED_STUB_H
+
+#include "api/mbed.h"
+
+#endif

mbed.lib

@@ -0,0 +1 @@
+https://github.com/mbedmicro/mbed/#d2fd820e13d9b8321b64f57e0cfd44a3d3edde8f

tools/targets.py

@@ -79,7 +79,7 @@ class Target:
     @staticmethod
     @cached
     def get_json_target_data():
-        with open(os.path.join(os.path.dirname(os.path.abspath(__file__)), "targets.json"), "rt") as f:
+        with open(os.path.join(os.path.dirname(os.path.abspath(__file__)), "../mbed/hal/targets.json"), "rt") as f:
             return Target.to_ascii(json.load(f))
 
     # Get the members of this module using Python's "inspect" module