EDIT-BLOCKFILE
 will load the edit module in the background and look for a word
 called EDIT-BLOCK that could be used to edit the blockfile.
 If no >EDIT-BLOCKFILE word can be loaded, nothing will happen.
 Otherwise, OPEN-BLOCKFILE is called followed by 0 EDIT-BLOCK
 to start editing the file at the first block.
  |     misc   ordinary primitive   |