The migration to struct stat_ex broke the calculation of

The migration to struct stat_ex broke the calculation of
create time from the existing timestamps (for systems
that need to do this). Once the write time is changed
via a sticky write, the create time might need to be
recalculated. To do this I needed to add a bool into
struct stat_ex to remember if the st_ex_btime field
was calculated, or read from the OS. Also fixed the
returning of modified write timestamps in the return
from NTCreateX, SMBattr and SMBattrE (which weren't
taking into account the modified timestamp stored
in the open file table). Attempting to fix an issue
with Excel 2003 and offline files. Volker and Metze,
please review.
Jeremy