Bug YYY - Part 1: Import Android PreferenceFragment.

This import is a modification of the commit with SHA
e9d370003c795fb7c023c50c53e707c97645d3ba developed at

https://github.com/kolavar/android-support-v4-preferencefragment

The original code is licensed Apache 2.0.

This code references Android resources so it cannot be exported into
mobile/android/thirdparty, since that code builds without an R.java in
scope.
Bug 915312 - TO BE FOLDED: Remove pbkdf2SHA1.
Bug 915312 - TO BE FOLDED: Allocate less.
Bug 915312 - Part 2: Add NativeCrypto exposing pbkdf2SHA256.
Bug 915312 - TO BE FOLDED: Allocate even less.