sync: latest libbpf changes from kernel

Syncing latest libbpf commits from kernel repository.
Baseline commit:   f01a7dbe98ae4265023fa5d3af0f076f0b18a647
Checkpoint commit: dd399ac9e343c7573c47d6820e4a23013c54749d

Arnaldo Carvalho de Melo (1):
  tools lib bpf: Fix the build by adding a missing stdarg.h include

Changbin Du (1):
  perf tools: Fix errors under optimization level '-Og'

Daniel Borkmann (1):
  bpf, libbpf: clarify bump in libbpf version info

Lorenz Bauer (1):
  tools: update include/uapi/linux/bpf.h

Luca Boccassi (1):
  tools/bpf: generate pkg-config file for libbpf

Song Liu (1):
  tools lib bpf: Introduce bpf_program__get_prog_info_linear()

Willem de Bruijn (1):
  bpf: Sync bpf.h to tools

 include/uapi/linux/bpf.h |  65 +++++++++-
 src/README.rst           |   1 +
 src/libbpf.c             | 253 ++++++++++++++++++++++++++++++++++++++-
 src/libbpf.h             |  64 ++++++++++
 src/libbpf.map           |   3 +
 src/libbpf.pc.template   |  12 ++
 6 files changed, 393 insertions(+), 5 deletions(-)
 create mode 100644 src/libbpf.pc.template

--
2.17.1

CHECKPOINT-COMMIT

@@ -1 +1 @@
-8543e437807970166c2b66b79935c9f4b0e6d1f9
+dd399ac9e343c7573c47d6820e4a23013c54749d