removing no longer used redefine_function

functions/redefine_function.fish

-function redefine_function -d "Redefine a function and backup the old using the prefix 'old_'"
-  if not set -q argv[1]; _print_error 'Missing function name argument.'; return 1; end
-  if not set -q argv[2]; _print_error 'Missing original function file argument.'; return 1; end
-  if not set -q argv[3]; _print_error 'Missing function code argument.'; return 1; end
-
-  _backup_old_function $argv
-  _load_new_function $argv
-end
-
-function _backup_old_function
-  set -l funcname $argv[1]
-  set -l funcfile $argv[2]
-
-  if test -f $funcfile
-    . $funcfile
-    functions -c $funcname old_$funcname
-  else
-    _print_error "File '$funcfile' not found"
-    return 1
-  end
-end
-
-function _load_new_function
-  set -l func $argv[3]
-
-  set -q TMPDIR; or set -l TMPDIR /tmp
-  set -l tmpname (printf "$TMPDIR/fish_funced_%d_%d.fish" %self (random))
-  while test -f $tmpname
-    set tmpname (printf "$TMPDIR/fish_funced_%d_%d.fish" %self (random))
-  end
-
-  echo $func > $tmpname
-  . $tmpname
-  rm $tmpname >/dev/null
-end
-
-function _print_error
-  set_color red
-  echo $argv
-  set_color normal
-end