build: removed unused and old option on AIX
android: add support of ifaddrs in android

In order to address https://github.com/joyent/node/issues/7291

* The original source code has been taken from
https://github.com/kmackay/android-ifaddrs
* Marking to be included only when OS==android in uv.gyp
* Updating linux-core accordingly, including the appropriate header only
when we're buliding for Android
* Updating configure.ac and Makefile.am accordingly
* Updating LICENSE
* Making the code ISO C90 compliant