node: Add support for android

Adds an ANDROID define and resolves minor discrepancies between
android and standard POSIX systems. In addition, some configure
parameters were added, and a helper-script for android configuration.
Ideally, this script should next be merged into the standard
configure script.

Note: This depends on the respective pull-requests in uv and cares:
https://github.com/joyent/libuv/pull/825
https://github.com/piscisaureus/cares/pull/2

To build for android, source the android-configure script
with an NDK path:

> source ./android-configure ~/android-ndk-r8d

This will create an android standalone toolchain and export the
necessary commands.

After that, build as normal:

> make -j8

After the build, you should now have android-compatible NodeJS
binaries.