ANDROID: Modify configure script for multi architecture builds.

The host targets for Android ARM builds are changed to "android-arm"
and "android-arm-v7a", from "android" and "android-v7a", and two new
targets are added of "android-mips" for MIPS and "android-x86" for
x86.

The older "android" and "android-v7a" targets are still supported,
but are deprecated.