build: add android support

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 be merged into
the standard configure script.

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 environment parameters.

After that, build as normal:

    make -j8

After the build, you should now have android-compatible NodeJS binaries.