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!

README

@@ -39,7 +39,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*| hostname        non-posix                    none
 =*  kill            yes                          none
 =*| link            yes                          none
-=*  ln              yes                          none
+=*| ln              yes                          none
 =*  logger          yes                          none
 =*  logname         yes                          none
 =   ls              no                           (-C), -S, -f, -m, -s, -x