Import magic.h from Linux 6.9 to get the definition of
BCACHEFS_SUPER_MAGIC. Update filesystems-gperf.gperf to add knowledge of
bcachefs.
This fixes the following error building against a bleeding edge kernel.
```
src/basic/meson.build:234:8: ERROR: Problem encountered: Unknown filesystems defined in kernel headers:
Filesystem found in kernel header but not in filesystems-gperf.gperf: BCACHEFS_SUPER_MAGIC
```
It's great that we provide fallback values, but if we got one of those wrong,
it could be a long time before anyone noticed. So let's add asserts that the
our internal defines actually match the official ones, when the latter are
available.
I did not add '#include "macro.h"' to missing_{audit,capability}, because
those are processed by an awk script that would need additional include
directories and could be confused by the additional lines. We don't include
those headers standalone anyway, so this is not necessary anyway.
Kernel commit cb12fd8e0dabb9a1c8aef55a6a41e2c255fcdf4b added pidfs.
Update filesystems-gperf.gperf and missing_magic.h accordingly.
This fixes the following error building against a bleeding edge kernel.
```
../src/basic/meson.build:234:8: ERROR: Problem encountered: Unknown filesystems defined in kernel headers:
Filesystem found in kernel header but not in filesystems-gperf.gperf: PID_FS_MAGIC
```
Kernel commit dea2903719283c156b53741126228c4a1b40440f exposed (and
renamed) CIFS_MAGIC_NUMBER as CIFS_SUPER_MAGIC along with
SMB2_SUPER_MAGIC.
This fixes the following build fail on current Fedora Rawhide:
```
../src/basic/meson.build:389:8: ERROR: Problem encountered: found unknown filesystem(s) defined in kernel headers:
Filesystem found in kernel header but not in filesystems-gperf.gperf: CIFS_SUPER_MAGIC
Filesystem found in kernel header but not in filesystems-gperf.gperf: SMB2_SUPER_MAGIC
```
devtmpfs and cpuset are not actual filesystems of their own. cpuset used
to be but is now an alias for cgroupsfs. devtmpfs is the same as tmpfs
as its just a "named superblock", i.e. a specific instance of tmpfs, but
not a file system of its own.
