first step at implementing the native sensor support

in this commit:
- implemented the C stub
- implemented the binder interfaces involved
- implemented most of the C++ client side

missing:
- SensorManager cannot connect to the SensorServer yet
(because there is no SensorServer yet)

Change-Id: I75010cbeef31c98d6fa62fd5d388dcef87c2636b
diff --git a/native/android/Android.mk b/native/android/Android.mk
index 509a379..2fe0679 100644
--- a/native/android/Android.mk
+++ b/native/android/Android.mk
@@ -9,13 +9,15 @@
     input.cpp \
     looper.cpp \
     native_activity.cpp \
-    native_window.cpp
+    native_window.cpp \
+    sensor.cpp
 
 LOCAL_SHARED_LIBRARIES := \
     libcutils \
     libutils \
     libbinder \
     libui \
+    libgui \
     libsurfaceflinger_client \
     libandroid_runtime