INT 21 - DOS 1+ - FIND FIRST MATCHING FILE USING FCB
        AH = 11h
        DS:DX -> unopened FCB (see AH=0Fh), may contain '?' wildcards
Return: AL = status
            00h successful
                [DTA] unopened FCB for first matching file
            FFh no matching filename, or bad FCB
Notes:  the type of the returned FCB depends on whether the input FCB was a
          normal or an extended FCB
        for extended FCBs with search attribute 08h, the volume label (if any)
          will be returned even if the current directory is not the root dir.
        DOS 3+ also allows the '*' wildcard
        the search FCB must not be modified if AH=12h will be used to continue
          searching; DOS 3.3 has set the following parts of the FCB:
                 0Ch    BYTE    ???
                 0Dh    WORD    directory entry number of matching file
                 0Fh    WORD    cluster number of current directory
                 11h  4 BYTEs   ???
                 15h    BYTE    drive number (1=A:)
        at least for DOS 3.3, the unopened FCB in the DTA is actually the drive
          number followed by the file's directory entry
SeeAlso: AH=1Ah,AH=4Eh,INT 2F/AX=111Bh