Remove the DUNE_SYMLINK macro.

It has been deprecated at least since dune 2.0.

[[Imported from SVN: r6482]]

m4/dune.m4

@@ -491,41 +491,3 @@ AC_DEFUN([DUNE_CHECK_MODULES],[
   # restore previous language settings (leave C++)
   AC_LANG_POP([C++])
 ])
-
-AC_DEFUN([DUNE_SYMLINK],[
-  AC_PROG_LN_S
-  AC_MSG_WARN([Module is using the deprecated 'dune' symlink.])
-  # create symlink for consistent paths even when $(top_srcdir) is not
-  # called dune/ (if filesystem/OS supports symlinks)
-  AS_IF([test "x$LN_S" = "xln -s"],[
-    # Symlinks possible!
-
-    # Note: we are currently in the build directory which may be != the
-    # source directory
- 
-    # does a file already exist?
-    AS_IF([test -e "dune"],[
-      # exists: is a symlink?
-      AS_IF([test -L "dune"],[
-        AS_IF([! test -r dune/$ac_unique_file],[
-          AC_MSG_ERROR([Symlink 'dune' exists but appears to be wrong! Please remove it manually])
-        ])
-      ],[
-        # if we are in the source directory we can make sure that there is no directory
-        AC_MSG_ERROR([Module is using the DUNE[]_SYMLINK directive but contains a directory 'dune'!])
-      ])
-    ],[
-      echo Creating dune-symlink...
-      # set symlink in build directory to sources
-      ln -s $srcdir dune
-
-      # sanity check
-      AS_IF([! test -r "dune/$ac_unique_file"],[
-        AC_MSG_ERROR([Sanity check for symlink failed! Please send a bugreport to dune@dune-project.org])
-      ])
-    ])
-  ],[
-    # no symlinks possible... check name of directory
-    AC_MSG_ERROR([No symlinks supported! You have to install dune. No inplace usage possible!])
-  ])
-])