Compatibility: 3.0+
Expects: AX    1000H
                                                                  
Returns: AL    status: 00H = is not installed
ffH = is installed
                                                                  
Info: Checks to see if the DOS SHARE.EXE program (which provides file-
locking functions) has been executed and is resident in memory.

Notes: Windows (and maybe others) intercept this vector and always
return a non-zero.

To really check to see if file-sharing support is installed, try
locking a file via DOS fn 5cH and check the error/return code.

- -

INT 2fH 1000H: Is Share.Exe Installed?