Fixes to use lfs_filebd on windows platforms

There are two issues, when using the file-based block device emulation
on Windows Platforms:
1. There is no fsync implementation available. This needs to be mapped
   to a Windows-specific FlushFileBuffers system call.
2. The block device file needs to be opened as binary file (O_BINARY)
	   The corresponding flag is not required for Linux.

bd/lfs_filebd.c

@@ -10,6 +10,10 @@
 #include <unistd.h>
 #include <errno.h>
 
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
 int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
         const struct lfs_filebd_config *bdcfg) {
     LFS_FILEBD_TRACE("lfs_filebd_createcfg(%p {.context=%p, "
@@ -27,7 +31,12 @@ int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
     bd->cfg = bdcfg;
 
     // open file
+    #ifdef _WIN32
+    bd->fd = open(path, O_RDWR | O_CREAT | O_BINARY, 0666);
+    #else
     bd->fd = open(path, O_RDWR | O_CREAT, 0666);
+    #endif
+
     if (bd->fd < 0) {
         int err = -errno;
         LFS_FILEBD_TRACE("lfs_filebd_createcfg -> %d", err);
@@ -193,7 +202,11 @@ int lfs_filebd_sync(const struct lfs_config *cfg) {
     LFS_FILEBD_TRACE("lfs_filebd_sync(%p)", (void*)cfg);
     // file sync
     lfs_filebd_t *bd = cfg->context;
+    #ifdef _WIN32
+    int err = FlushFileBuffers((HANDLE) _get_osfhandle(fd)) ? 0 : -1;
+    #else
     int err = fsync(bd->fd);
+    #endif
     if (err) {
         err = -errno;
         LFS_FILEBD_TRACE("lfs_filebd_sync -> %d", 0);