MFC r319855,r319856,r319858:

r319855:

Use readlink(1)/stat(1) to query symlinks instead of file(1)

file(1) can be compiled out of the system via MK_FILE == no, and the
output isn't guaranteed to be stable. It's better to use stat(1)/readlink(1)
instead to query symlink/file paths.

MFC with: r319714, r319854

r319856:

Add a testcase for ln -sF

The testcase fails today, so mark it with atf_expect_fail: in
particular, the target (B) isn't being unlinked and the documentation
doesn't suggest special handling for directories. Thus, there's either
a doc or an implementation bug in ln(1) that needs to be resolved.

MFC with: r319714, r319854, r319855
PR: 219943

r319858:

Style fixes: clean up leading whitespace (8 single column spaces -> \t)

MFC with: r319714, r319854, r319855, r319856