[android][4.4.2_r2]compiling libnative_camera_r4.4.2.so for nx5
1. cd aosp_4.4.2_r2
2. . build/envsetup.sh
3. lunch 6 (hammerhead)
now you have aosp env ready,
"cp development/sdk/platform_source.prop_template development/sdk/platform_source.properties"
Replace the env vars in the platform_source.properties by the real value.

*NOTE: if you don't want to build libnative_camera, don't run the aosp env setup,
but let openCV to find your ADT and NDK, otherwise android sample app won't be built due to the wrong sdk version in AOSP prebuilt tools.

4. cd openCV/platforms
5. sh scripts/cmake_android_arm.sh
6. cd build_android_arm
7. make -j8
8. you will find lib/armeabi-v7a/libnative_camera_r4.4.2.so
9. copy to openCV/3rdparty/lib/armeabi-v7a