Allows a process to change the protection on a page or range of
    pages.

    Format

      SYS$SETPRT  inadr ,[retadr] ,[acmode] ,prot ,[prvprt]

    C Prototype

      int sys$setprt  (struct _va_range *inadr, struct _va_range

                      *retadr, unsigned int acmode, unsigned int

                      prot, unsigned char *prvprt);