LOCK: lock keyboard e.g. in process control applications (H)

The LOCK function locks the keyboard while the script is running. It unlocks when the locking key is hit on the keyboard.
- ascii_number_of_key = LOCK( locking_key_character )
the explicit result of LOCK is ICHAR("locking_key_character ")
unlocking the keyboard by a script command is by locking_key_character = space:
```
 LOCK(" ")
```

the KEY(...) function still accepts keyboard input, e.g.:

 LOCK("+") 
 DO i = 1, 1E100 ! "forever" 
    KEY(Ascii=a) ! a is set to 0 if no key was pressed 
    IF(a) WRITE(Messagebox,Name) a ! or any other action 
 ENDDO ! execution can be broken by Escape only afte "+" was hit

locking_key_character" is case sensitive
another example:
- key_nr = LOCK("A") ! key_nr is set to 65. Unlock by by pressing capital "A" on the keyboard