Add dockerfile and build script for Android.

Dockerfile.android

+FROM ubuntu:16.04
+MAINTAINER PaddlePaddle Authors <paddle-dev@baidu.com>
+
+ARG UBUNTU_MIRROR
+RUN /bin/bash -c 'if [[ -n ${UBUNTU_MIRROR} ]]; then sed -i 's#http://archive.ubuntu.com/ubuntu#${UBUNTU_MIRROR}#g' /etc/apt/sources.list; fi'
+
+ENV HOME=/root \
+    ANDROID_HOME=/opt/android-sdk-linux \
+    ANDROID_NDK_HOME=/opt/android-ndk-linux \
+    ANDROID_STANDALONE_TOOLCHAIN=/opt/android-toolchain-gcc \
+    PATH=${PATH}:${ANDROID_HOME}:${ANDROID_NDK_HOME}
+
+RUN apt-get update && \
+    apt-get install -y git python-dev python-pip python-numpy && \
+    apt-get install -y wget curl tar unzip && \
+    apt-get install -y gcc g++ locales swig && \
+    apt-get clean -y
+
+RUN pip install --upgrade pip && \
+    pip install -U 'protobuf==3.1.0' && \
+    pip install -U wheel sphinx && \
+    pip install pre-commit
+
+# git credential to skip password typing
+RUN git config --global credential.helper store
+
+# Fix locales to en_US.UTF-8
+RUN localedef -i en_US -f UTF-8 en_US.UTF-8
+
+RUN curl -sSL https://cmake.org/files/v3.2/cmake-3.2.2.tar.gz | tar -xz && \
+    cd cmake-3.2.2 && ./bootstrap && make -j `nproc` && make install && \
+    cd .. && rm -rf cmake-3.2.2
+
+# Android NDK
+RUN mkdir /opt/android-ndk-tmp && \
+    cd /opt/android-ndk-tmp && \
+    wget -q https://dl.google.com/android/repository/android-ndk-r14b-linux-x86_64.zip && \
+    unzip -q android-ndk-r14b-linux-x86_64.zip && \
+    mv android-ndk-r14b ${ANDROID_NDK_HOME} && \
+    ${ANDROID_NDK_HOME}/build/tools/make-standalone-toolchain.sh --arch=arm --platform=android-21 --install-dir=${ANDROID_STANDALONE_TOOLCHAIN} && \
+    rm -rf /opt/android-ndk-tmp
+
+CMD ["bash", "paddle/paddle/scripts/docker/build_android.sh"]

paddle/scripts/docker/build_android.sh

+#!/bin/bash
+
+set -xe
+
+mkdir -p /paddle/build
+cd /paddle/build
+cmake -DCMAKE_SYSTEM_NAME=Android \
+      -DANDROID_STANDALONE_TOOLCHAIN=$ANDROID_STANDALONE_TOOLCHAIN \
+      -DANDROID_ABI=armeabi-v7a \
+      -DANDROID_ARM_NEON=ON \
+      -DANDROID_ARM_MODE=ON \
+      -DHOST_C_COMPILER=/usr/bin/gcc \
+      -DHOST_CXX_COMPILER=/usr/bin/g++ \
+      -DCMAKE_INSTALL_PREFIX=/paddle/install \
+      -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+      -DCMAKE_C_FLAGS_RELWITHDEBINFO="-O3" \
+      -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-O3" \
+      -DWITH_C_API=ON \
+      -DWITH_SWIG_PY=OFF \
+      ..
+make -j `nproc`
+make install
+
+export PATH=/paddle/install/bin:/paddle/install/opt/paddle/bin:$PATH
+paddle version