Fix Windows os_dir.c, and os_ftruncate.c. Correctly enable hardware chksum

Fix Windows os_dir.c. @michaelcahill was correct that this function was not returning the correct list of files. I need to append *. I used a WT_ITEM for the buffer. Let me know if you would like me to change it.

Fix missing return in os_ftruncate.c.
Correctly enable hardware chksum. I had disabled debugging a chksum error which had nothing to do with the chksum code.