Audit readlink(1)

1) Properly document e, f and m-flags in the manpage.
2) Clear up the code for the m-flag-handling. Add idiomatic
   '/'-path-traversal as already seen in mkdir(1).
3) Unwrap the SWAP_BUF()-macro.
4) BUGFIX: Actually handle the f-flag properly. Only resolve
   the dirname and append the basename later.
5) Use fputs() instead of printf("%s", ...).

README

@@ -55,7 +55,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*| printenv        non-posix                    none
 #*| printf          yes                          none
 =*| pwd             yes                          none
-=   readlink        non-posix                    none
+=*| readlink        non-posix                    none
 =*| renice          yes                          none
 =*| rm              yes                          none (-i)
 =*| rmdir           yes                          none