Audit ln(1)

1) Clarify behaviour when the f-flag is given and a target is in its
   own way.
2) Fix usage()-style.
3) Group local variable declarations.
4) reorder args
5) argc style, other boolean style changes
6) improve error messages
7) set argv[argc - 1] to NULL to allow argv-centric loop later
8) BUGFIX: POSIX specifies that when with the f-flag there's a
   situation where a file stands in its own way for linking it
   should be ignored.
9) Add weprintf() where possible, so we don't pussy out when there's
   a small issue. This is sbase ffs!

ln.1

@@ -1,4 +1,4 @@
-.Dd January 26, 2015
+.Dd March 5, 2015
 .Dt LN 1
 .Os sbase
 .Sh NAME
@@ -37,7 +37,9 @@ hardlinks them in the existing
 .It Fl f
 If
 .Ar name
-exists, remove it to allow the link.
+exists and is not a
+.Ar target ,
+remove it to allow the link.
 .It Fl L | Fl P
 If
 .Ar target