Add support for inode/* MIME types in DetectFile

[gabriel-vasile]

Only for DetectFile, inode/* MIME types could be detected.

inode/blockdevice
inode/chardevice
inode/directory
inode/fifo
inode/mount-point
inode/socket
inode/symlink

How to implement: with a call to stat before doing actual detection
https://github.com/file/file/blob/master/src/fsmagic.c

[gabriel-vasile]

It's unclear whether this is a useful feature. Both file and magika provide it, but they are more CLIs than they are libraries.

Reasons against it:

• can be implemented only for DetectFile. Not for DetectReader and Detect
• no one asked for it since the library was created
• introduces complexity: the inode/* cannot be regular mime types because they are not based on the content of the file, rather on the unix file flags. Right now, detection functions only receive the content of the file as input. Either the detection functions will be updated, or a pre-detection step will be introduced into DetectFile to implement this feature.