Merge branch 'bpftool-match-by-name'

Paul Chaignon says:

====================
When working with frequently modified BPF programs, both the ID and the
tag may change.  bpftool currently doesn't provide a "stable" way to match
such programs.  This patchset allows bpftool to match programs and maps by
name.

When given a tag that matches several programs, bpftool currently only
considers the first match.  The first patch changes that behavior to
either process all matching programs (for the show and dump commands) or
error out.  The second patch implements program lookup by name, with the
same behavior as for tags in case of ambiguity.  The last patch implements
map lookup by name.

Changelogs:
  Changes in v2:
    - Fix buffer overflow after realloc.
    - Add example output to commit message.
    - Properly close JSON arrays on errors.
    - Fix style errors (line breaks, for loops, exit labels, type for
      tagname).
    - Move do_show code for argc == 2 to do_show_subset functions.
    - Rebase.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>