net: core: Support UID-based routing.

This contains the following commits:

1. 0149763 net: core: Add a UID range to fib rules.

2. 1650474 net: core: Use the socket UID in routing lookups.

3. 0b16771 net: ipv4: Add the UID to the route cache.

4. ee058f1 net: core: Add a RTA_UID attribute to routes.

    This is so that userspace can do per-UID route lookups.

Bug: 15413527

Change-Id: I1285474c6734614d3bda6f61d88dfe89a4af7892

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

Git-commit: 0b428749ce5969bc06c73855e360141b4e7126e8

Git-repo: https://android.googlesource.com/kernel/common.git

Signed-off-by: Ian Maund <imaund@codeaurora.org>