libports: add libc_fuse_ntfs-3g
libports: initial fuse_fs implementation
os: extentend File_system interface with sync RPC
add sync implementation to various fs servers
noux: add SYSCALL_SYNC

File systems using the File_system_session interface can now be
synchronized by using this syscall. This is needed for file system
that maintain an internal cache, which should be flushed.