userlandfs: implement get_fs_info using ioctl

This avoids introducing an entirely custom hook in FUSE.
It uses the ioctl hook in an unconventional way (calling it with no
valid fuse_file_info) but this can be fixed if a filesystem requires it
(by opening a file handle on /, doing the ioctl, then closing again).

An updated version of fusesmb-haiku is available and confirmed working:
https://github.com/haikuarchives/fusesmb-haiku

Change-Id: If1268113874363fa035e5340be75e9f5198216d6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5199
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

userlandfs: compatibility with FUSE 2.9 and FUSE lowlevel API

- Import latest version of files from FUSE 2.9.9 (our last
synchronization was with 2.7.4)
- Adjust fuse pkgconfig file to use the POSIX error mapper
automatically, since that's required for all FUSE software
- Implement the lowlevel API in addition to the highlevel one. The
lowlevel API uses inode numbers to identify files, rather than paths,
making it a better fit to the userlandfs architecture.

The FUSE 2.x branch is not maintained anymore by FUSE developers,
however, pretty much no one migrated to FUSE 3.x. So it is more
interesting to implement, rather than 3.x.

Confirmed still working with sshfs and curlftpfs.

Example use:

I tested this with github.com/whoozle/android-file-transfer-linux

- Build the fuse library and copy it to ~/config/non-packaged/add-ons/userlandfs/
- Start the server: /system/servers/userlandfs_server aft-mtp-mount
- Connect your Android phone and put it in USB file transfer mode
- Mount the device: mount -t userlandfs -p 'aft-mtp-mount /boot/home/MyPhone -d -o use_ino' ~/MyPhone
- You can now access your phone data

Change-Id: Ic3efda7ffbc33737e6f4958428fb3ec9939ef105
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5198
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

FUSE compat: add Haiku extension

* Add a way for a FUSE module to supply Haiku-specific extensions.
This allows it to integrate better with Haiku while only requiring
minimal changes on the FUSE module itself.

* For now, there is only one extension: another function pointer for
"get_fs_info", which lets the FUSE module fill in an fs_info struct.
FUSE provides no good way to otherwise communicate extra information,
such as the volume flags (e.g. B_FS_IS_SHARED).

* A FUSE module can signal that it supports the Haiku extensions by
a) defining HAS_HAIKU_FUSE_EXTENSIONS before including the fuse
headers
b) setting the global variable gHasHaikuFuseExtensions to 1 in
its initialization
Otherwise, the Haiku extensions are completely invisible to the
FUSE module.

Imported FUSE 2.7.4 includes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29592 a95241bf-73f2-0310-859d-f6bbb57e9c96

Imported FUSE 2.7.4 includes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29592 a95241bf-73f2-0310-859d-f6bbb57e9c96