bpftool: support loading flow dissector

v5 changes:
* FILE -> PATH for load/loadall (can be either file or directory now)
* simpler implementation for __bpf_program__pin_name
* removed p_err for REQ_ARGS checks
* parse_atach_detach_args -> parse_attach_detach_args
* for -> while in bpf_object__pin_{programs,maps} recovery

v4 changes:
* addressed another round of comments/style issues from Jakub Kicinski & Quentin Monnet (thanks!)
* implemented bpf_object__pin_maps and bpf_object__pin_programs helpers and used them in bpf_program__pin
* added new pin_name to bpf_program so bpf_program__pin
works with sections that contain '/'
* moved *loadall* command implementation into a separate patch
* added patch that implements *pinmaps* to pin maps when doing load/loadall

v3 changes:
* (maybe) better cleanup for partial failure in bpf_object__pin
* added special case in bpf_program__pin for programs with single instances

v2 changes:
* addressed comments/style issues from Jakub Kicinski & Quentin Monnet
* removed logic that populates jump table
* added cleanup for partial failure in bpf_object__pin

This patch series adds support for loading and attaching flow dissector programs from the bpftool:

* first patch fixes flow dissector section name in the selftests (so libbpf auto-detection works)
* second patch adds proper cleanup to bpf_object__pin, parts of which are now being used to attach all flow dissector progs/maps
* third patch adds special case in bpf_program__pin for programs with single instances (we don't create <prog>/0 pin anymore, just <prog>)
* forth patch adds pin_name to the bpf_program struct
which is now used as a pin name in bpf_program__pin et al
* fifth patch adds *loadall* command that pins all programs, not just the first one
* sixth patch adds *pinmaps* argument to load/loadall to let users pin all maps of the obj file
* seventh patch adds actual flow_dissector support to the bpftool and an example

Stanislav Fomichev (7):
selftests/bpf: rename flow dissector section to flow_dissector
libbpf: cleanup after partial failure in bpf_object__pin
libbpf: bpf_program__pin: add special case for instances.nr == 1
libbpf: add internal pin_name
bpftool: add loadall command
bpftool: add pinmaps argument to the load/loadall
bpftool: support loading flow dissector

 .../bpftool/Documentation/bpftool-prog.rst    |  42 +-
 tools/bpf/bpftool/bash-completion/bpftool     |  21 +-
 tools/bpf/bpftool/common.c                    |  31 +-
 tools/bpf/bpftool/main.h                      |   1 +
 tools/bpf/bpftool/prog.c                      | 183 ++++++---
 tools/lib/bpf/libbpf.c                        | 359 ++++++++++++++++--
 tools/lib/bpf/libbpf.h                        |  18 +
 tools/testing/selftests/bpf/bpf_flow.c        |   2 +-
 .../selftests/bpf/test_flow_dissector.sh      |   2 +-
 9 files changed, 537 insertions(+), 122 deletions(-)

2.19.1.930.g4563a0d9d0-goog