file_stat() on NT ought to consider settings in the register.
Imported from https://youtrack.roxen.com/issue/PIKE-99
Reported by @grubba
Match the file suffix against the values listed by
{{RegGetKeyNames(HKEY_CURRENT_USER, "Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts");}}
to set the X-bit in st_mode
or not.