libbinder_ndk: linkToDeath/unlinkToDeath

This adds AIBinder_DeathRecipient and methods to use it in order
to receive death notifications.

Bug: 111445392
Test: ./ndk/runtests.sh
Test: manually killing a service and finding its death recipient

Change-Id: I556435cae88b01e6e2cfdc0a286bdb660859872c