[BTRFS][UBTRFS][SHELLBTRFS] Upgrade to 1.7.6 (#4417)

v1.7.6 (2021-01-14):

- Fixed race condition when booting with Quibble
- No longer need to restart Windows after initial installation
- Forced maximum file name to 255 UTF-8 characters, to match Linux driver
- Fixed issue where directories could be created with trailing backslash
- Fixed potential deadlock when Windows calls NtCreateSection during flush
- Miscellaneous bug fixes

sdk/lib/fslib/btrfslib/btrfslib.c

@@ -1263,13 +1263,6 @@ static bool is_mounted_multi_device(HANDLE h, uint32_t sector_size) {
         bfs = malloc(bfssize);
 
         Status = NtDeviceIoControlFile(h2, NULL, NULL, NULL, &iosb, IOCTL_BTRFS_QUERY_FILESYSTEMS, NULL, 0, bfs, bfssize);
-        if (!NT_SUCCESS(Status) && Status != STATUS_BUFFER_OVERFLOW) {
-#ifdef __REACTOS__
-            if (bfs) free(bfs);
-#endif
-            NtClose(h2);
-            return false;
-        }
     } while (Status == STATUS_BUFFER_OVERFLOW);
 
     if (!NT_SUCCESS(Status))