libfuse: document deadlock avoidance for fuse_notify_inval_entry()

and fuse_notify_delete()

Reported by Han-Wen Nienhuys
fusermount, libfuse: send value as unsigned in "user_id=" and "group_id="

...options.  Uids/gids larger than 2147483647 would result in EINVAL when
mounting the filesystem.  This also needs a fix in the kernel.
libfuse: add "time_gran" option

This allows the filesystem to specify the time granularity it
supports when the kernel is responsible for updating times
("writeback_cache" option).
libfuse: allow setting ctime in ->setattr()
libfuse: add flags to ->rename()

See renameat2() system call in linux-3.15 and later kernels.
ChangeLog fix
libfuse: highlevel API: fix directory file handle passed to ioctl() method

Reported by Eric Biggers