The goal is to fully support FUSE API version 3.0 while maintaining
API/ABI compatibility with code written for 2.6 (or even older).
* <fuse.h> now emits a compiler warning if it's included without
defining FUSE_USE_VERSION. It had been silently defaulted to the
latest supported version prior to this change. This is permissive
compared to the original FUSE, as it emits an error instead.
* <fuse.h> now emits a warning if FUSE_USE_VERSION is higher than what
can be provided.
* Added a macro FUSE_MAKE_VERSION(maj, min). It was missing from
librefuse <fuse.h>.
No actual API updates have been made (yet).