Fix broken but working code in XFD support

Originally reported by Fredrik Wikstrom:

"While looking for some XFD example code I happened upon the XMP XFD code
 written by you and found some broken code in it:

 xfdobj->xfdbi_Flags = XFDFB_RECOGEXTERN | XFDFB_RECOGTARGETLEN;

 This code is incorrect because bit numbers (XFDFB_#?) are used instead
 of bit masks (XFDFF_#?).

 As the value of XFDFB_RECOGEXTERN is 0 and the value of
 XFDFB_RECOGTARGETLEN is 1 which coincidentally happens to be the same as
 XFDFF_RECOGEXTERN the code is working, but only by accident.

 Also I don't see why the code sets xfdbi_PackerFlags to XFDPFB_RECOGLEN
 (also same error here as before). As xfdRecogBuffer() simply overwrites
 this value this doesn't hurt but it doesn't do anything useful either."

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>