VFS Stat modes should include FIFO to match Dirent types

Currently, the VFS Dirent types listed in repos/os/include/vfs/directory_service.h include FIFO, while the Stat modes do not. I'm writing a transparent link VFS plugin, so I'm using stat() for the Dirent information, so I need this feature in order to avoid losing information. I'm also writing a FIFO plugin, so I want it to accurately represent itself. The FreeBSD libc includes FIFO as S_IFIFO = 0010000.

Until this is added, I'll add the constant to my own files, but I'd much rather have this included in vfs/directory_service.h.