The JS str_cmds has the following functions known to be broken and/or
unimplementable:
;MEM		- Also not implemented in BAJA.
;UPLOAD		- Uses bbs.bulk_upload() but seems to not work
;RESORT		- Assumes (incorrectly) that bbs.curlib and bbs.curdir are
                  indexes into file_area.lib_list and
                  file_area.lib_list.dir_list respectively.
;OLDUL		- In progress (Not done)
;OLD		- In progress (Not done)
;OFFLINE	- In progress (Not done)
;CLOSE		- In progress (Not done)
;GET		- FILE_GET not implemented under JS
;PUT		- FILE_PUT not implemented under JS

Added a ;NEXEC command to execute that parameter as a NATIVE binary.
The node utility is now only called for the ;NODE command.
The comspec is not JS exposed, so a kludge is used for ;SHELL.