sync: latest libbpf changes from kernel

Syncing latest libbpf commits from kernel repository.
Baseline commit:   ea5bade929bf04355aeed58a3c9f5ef2c3afe2ac
Checkpoint commit: f01a7dbe98ae4265023fa5d3af0f076f0b18a647

Andrii Nakryiko (2):
  libbpf: handle BTF parsing and loading properly
  btf: resolve enum fwds in btf_dedup

Magnus Karlsson (1):
  libbpf: fix to reject unknown flags in xsk_socket__create()

Martin KaFai Lau (1):
  bpf: Sync bpf.h to tools/

Nikita V. Shirokov (1):
  bpf, libbpf: fixing leak when kernel does not support btf

Quentin Monnet (1):
  tools: bpf: synchronise BPF UAPI header with tools

 include/uapi/linux/bpf.h | 188 ++++++++++++++++++++++++++-------------
 src/btf.c                |  51 ++++++++---
 src/libbpf.c             |  11 ++-
 src/xsk.c                |  15 +++-
 4 files changed, 186 insertions(+), 79 deletions(-)

--
2.17.1

CHECKPOINT-COMMIT

@@ -1 +1 @@
-ea5bade929bf04355aeed58a3c9f5ef2c3afe2ac
+f01a7dbe98ae4265023fa5d3af0f076f0b18a647