open.2: update description for O_PATH

- Add fstatfs(), fchdir(), fchroot(), extattr_*_fd(), cap_*_get(),
  cap_*_limit() to the list of syscalls that can take an O_PATH fd.
- Remove readlinkat() from the list, since it is already discussed
  in the first few lines of the paragraph.  It was originally added
  to the list when readlinkat() adds support for non-dir fd with
  an empty relative path (as if with AT_EMPTY_PATH), however,
  such use case is also discussed in the next paragraph.
- Add funlinkat() to the list, since it accepts an extra fd
  (of the file to be unlinked), which is worth extra mentioning.
- Fix a syntax issue which causes a bogus space to be rendered
  before a closing parentheses.

Signed-off-by: CismonX <admin@cismon.net>

Reviewed by:	markj, jhb
MFC after:	2 weeks
Pull Request:	freebsd#1564

lib/libsys/open.2

@@ -393,7 +393,12 @@ but advisory locking is not allowed
 .It Xr dup 2
 .It Xr close 2
 .It Xr fstat 2
+.It Xr fstatfs 2
+.It Xr fchdir 2
+.It Xr fchroot 2
 .It Xr fexecve 2
+.It Xr funlinkat 2
+can be passed as the third argument
 .It Dv SCM_RIGHTS
 can be passed over a
 .Xr unix 4
@@ -403,16 +408,23 @@ message
 .It Xr kqueue 2
 only with
 .Dv EVFILT_VNODE
-.It Xr readlinkat 2
 .It Xr __acl_get_fd 2
 .It Xr __acl_aclcheck_fd 2
+.It Xr extattr 2
+.It Xr capsicum 4
+can be passed to
+.Fn cap_*_limit
+and
+.Fn cap_*_get
+system calls (such as
+.Xr cap_rights_limit 2 ) .
 .El
 .Pp
 Other operations like
 .Xr read 2 ,
 .Xr ftruncate 2 ,
 and any other that operate on file and not on file descriptor (except
-.Xr fstat 2 ),
+.Xr fstat 2 ) ,
 are not allowed.
 .Pp
 A file descriptor created with the