HADFS Version number
BFNversionb returns the HADFS binary version number.  This is the version
number*100 for versions before 0.52 and version number*100 for versions
5.20 onwards, ie HADFS 0.48 returns 48 and HADFS 5.20 returns 52.

B    DEFFNversion:LOCAL A%,X%,Y%,E%
    A%=&FD:X%=&70:A%=USR&FFDA AND &FF:=((A%+3) AND &FF)-3

    REM Shorter version:
    DEFFNversion=((FNargs0(&FD,0)+3)AND &FF)-3b

The +3 and -3 are so that early version of HADFS, or non-HADFS filing
systems return a value of -3 so easy comparisons can be made, eg

B    IF FNversion<40 THEN PRINT "Must be HADFS 0.40 or later":ENDb