Causes the symbol symb to be dynamically loaded if it is called. symb can be either of:
symbol[, symbol]
:symbol-filename
where symbol is a function name and symbol-filename is a text file containing a list of symbols, one per line. Spaces between -d and ":" are allowed. There can be no spaces between ":" and the filename.
This option can be used when producing a linked executable module, to specify any missing modules that are to be loaded dynamically at run time.