Cross platform native resources support.

This commit unlocks mac and windows host support for the
AssetManager and ApkAssets JNI bindings.

Included in this change is:
- remove obsolete references to linux only headers like signal.h and
  linux/capability
- use the DupFdCloExec wrapper instead of fcntl calls directly
- Instead of using ParcelFileDescritor#adoptFd, create FileDescriptors
  via the constructor. This is not strictly necessary but it avoids
  use of the android-only FileDescriptor#setInt$ method.
- Also set the FileDescriptor.handle when on windows

Flag: NONE host-only change
Test: atest CtsResourcesTestCasesRavenwood
Change-Id: Ifd4090ca2c5cb746f88280f675b31642aec35769