contrib: add embedded libbpf 0.0.6

Knot.files

configure.ac

src/contrib/Makefile.inc

src/contrib/libbpf/LICENSE

src/contrib/libbpf/bpf/bpf.c

src/contrib/libbpf/bpf/bpf.h

src/contrib/libbpf/bpf/bpf_core_read.h

src/contrib/libbpf/bpf/bpf_endian.h

src/contrib/libbpf/bpf/bpf_helper_defs.h

src/contrib/libbpf/bpf/bpf_helpers.h

src/contrib/libbpf/bpf/bpf_prog_linfo.c

src/contrib/libbpf/bpf/bpf_tracing.h

src/contrib/libbpf/bpf/btf.c

src/contrib/libbpf/bpf/btf.h

src/contrib/libbpf/bpf/btf_dump.c

src/contrib/libbpf/bpf/hashmap.c

src/contrib/libbpf/bpf/hashmap.h

src/contrib/libbpf/bpf/libbpf.c

src/contrib/libbpf/bpf/libbpf.h

src/contrib/libbpf/bpf/libbpf_errno.c