* Fixed different not-in-sync #ifdef blocks for struct stat variants under Windows.
Comments have been left to indicate the portions of BLI_fileops.h and
BLI_fileops_types.h that need to stay in sync.
* Added BLI_wstat() to de-duplicate #ifdef blocks for stat() variants on Windows.
* Fix for opendir() and associate functions in MinGW not working properly with
non-ASCII, MBCS-compatible paths.
MinGW (FREE_WINDOWS) has opendir() and _wopendir(), and only the
latter accepts a path name of wchar_t type. Rather than messing up with
extra #ifdef's here and there, Blender's own implementations of opendir()
and related functions are used to properly support paths with non-ASCII,
MBCS-compatible characters.
Tested with MSVC 2013 Express, MinGW32 (gcc 4.6.2) and MinGW-w64 (gcc 4.7.1).
Differential Revision: https://developer.blender.org/D605
Reviewed By: campbellbarton
