pfctl: fix recrusive printing of anchors

Fix a couple of problems with printing of anchors, in particular recursive
printing, both of inline anchors and when requested explicitly with a '*'
in the anchor.

• Correct recursive printing of wildcard anchors (recurse into child anchors

rather than rules, which don't exist)

• Print multi-part anchor paths correctly (pr6065)
• Fix comments and prevent users from specifying multi-component names for

inline anchors.

tested by phessler
ok henning

Also fix the relevant pfctl test case to reflect the new (and now
correct) behaviour).

MFC after: 3 weeks
Obtained from: OpenBSD (mcbride, f9a568a27c740528301ca3419316c85a9fc7f1de)
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D36416

(cherry picked from commit 585a5ed0bef4a0b874c8fa495ae53901799759c3)