sync: latest libbpf changes from kernel

Syncing latest libbpf commits from kernel repository.
Baseline bpf-next commit:   0bb52b0dfc88a155688f492aba8e686147600278
Checkpoint bpf-next commit: b41dae061bbd722b9d7fa828f35d22035b218e18
Baseline bpf commit:        2c238177bd7f4b14bdf7447cc1cd9bb791f147e6
Checkpoint bpf commit:      e3439af4a339acd7fddbd6d59b8ecefaac07a611

Alexei Starovoitov (1):
  tools/bpf: sync bpf.h

Andrii Nakryiko (2):
  libbpf: fix false uninitialized variable warning
  libbpf: Teach btf_dumper to emit stand-alone anonymous enum
    definitions

Daniel Borkmann (1):
  bpf: sync bpf.h to tools infrastructure

Kevin Laatz (1):
  libbpf: add flags to umem config

Toke Høiland-Jørgensen (1):
  libbpf: Remove getsockopt() check for XDP_OPTIONS

 include/uapi/linux/bpf.h    |  7 ++-
 include/uapi/linux/if_xdp.h |  9 ++++
 src/btf_dump.c              | 94 ++++++++++++++++++++++++++++++++++---
 src/libbpf.map              |  1 +
 src/xsk.c                   | 44 +++++++++++------
 src/xsk.h                   | 27 +++++++++++
 6 files changed, 160 insertions(+), 22 deletions(-)

--
2.17.1

BPF-CHECKPOINT-COMMIT

@@ -1 +1 @@
-2c238177bd7f4b14bdf7447cc1cd9bb791f147e6
+e3439af4a339acd7fddbd6d59b8ecefaac07a611

CHECKPOINT-COMMIT

@@ -1 +1 @@
-0bb52b0dfc88a155688f492aba8e686147600278
+b41dae061bbd722b9d7fa828f35d22035b218e18