mimetypes for IFF and ILBM files

[Magnus Bergman]

I looked into how ILBM-images was handles in the shared-mime-info
package and found some information missing and some other I consider
wrong. I would gladly fix this, but I don't know the correct procedure.

There are currently two types defined (image/x-iff and image/x-ilbm),
these refer to the exact same format. Here is the full story:

IFF (Interchange Format File) if just a container format (created by
Electrinic Arts in 1985) which can contain different types of data.
There is many subtypes defined but most of them are only used in game
creation (such as sprite animation and game levels) and are quite rare.
These files can have many different extensions even for the same
subtype. I suggest that the mimetype should be application/x-iff.

  application/x-iff magic: string "FORM" at offset 0

There are two subtypes for common bitmaps, ILBM (Interlaced BitMap,
which was designed with the Amiga hardware in mind) and PBM (more suited
for PC hardware). Both subtypes are usually refered to as ilbm-files
(and all programs I know of consider them to be the same thing). So I
suggest the mimetype (for both subtypes) should be image/x-ilbm. The
common extensions for these files are ilbm, lbm and iff. Perhaps the iff
extension shouldn't be associated with ILBM-images since it makes sence
to use it for other types of IFF-files too (but for some reason only
ILBM-images seem to have this extension).

  image/x-ilbm magic: string "ILBM" or "PBM " at offset 8

AIFF (Audio Interchange Format File) is also a subtype if IFF, handled
correctly already.