Add Android AOSP Build System Makefile fragments and config files

Figured it would be nice to push this upstream so everyone/anyone can benefit from it. 

The Android.mk is apache licensed which is "Android's" standard license. 
I applied what appears to be your standard libarchive license to the header configs to avoid any license conflict/compatibility issues that more or may not exist between your license and any other. 

I added it to the contrib directory rather than the build so it doesn't add any support "burden" to yourselves.