Win32 dirent: change FILENAME_MAX to MAX_PATH

FILENAME_MAX and MAX_PATH are both 260 on Windows, however, MAX_PATH is
used throughout the other Win32 code in Git, and also defines the length
of file name buffers in the Win32 API (e.g. WIN32_FIND_DATA.cFileName,
from which we're copying the dirent data).

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/win32/dirent.h

@@ -9,8 +9,8 @@ typedef struct DIR DIR;
 #define DT_LNK     3
 
 struct dirent {
-	char d_name[FILENAME_MAX];       /* File name. */
 	unsigned char d_type;      /* file type to prevent lstat after readdir */
+	char d_name[MAX_PATH];     /* file name */
 };
 
 DIR *opendir(const char *dirname);