[interfacekit] __mime_table

Hi folks,

When writing the BMimeType::GetSupportingApps() tests, I decided to 
manually build my own supporting apps table and compare it to the 
information returned by GetSupportingApps(). The strange thing was, 
for certain types, GetSupportingApps() returned *more* app signatures 
than I had collected by compiling the META:FILE_TYPES attributes of 
all the "application/" types. Furthermore, I was finding app 
signatures that didn't even exist in my database.

I eventually discovered that this extra information was being taken 
from the file "__mime_table" in the root directory of the MIME 
database (which is just a flattened BMessage). The interesting thing 
is, if you change the __mime_table file (i.e. by unflattening it, 
adding to it, then re-flattening it), it 1) has no effect on 
GetSupportingApps() (not too surprising, the registrar probably 
caches it) but 2) is eventually (i.e. within a few minutes) restored 
to its original condition by some agent (again, assumingly the 
registrar). 

I assume, then, that somewhere there is an API (possibly just a 
message protocol to the roster/registrar) to make concrete changes to 
the __mime_table, as my __mime_table is larger than the __mime_table 
of a clean install, and contains entries from applications I once 
installed but have since removed (such as BeatWare Mail-It). Does 
anybody know about such an API (presumably from the olden days) off 
hand?

I suppose we ought to try to support this API if we want to be truly 
backwards compatible, but I don't currently have any great 
suggestions as to how we should go about this. I'm not going to put 
too much effort into it right now, as there are other things that 
need doing, but I thought I'd mention it here so we don't forget to 
possibly look into it at a later date. :-)

One other MIME related thing I should mention is that, while speaking 
with AnEvilYak a few weeks ago, he noted that the automatic MIME 
sniffer on his system never runs when he has something like SETI 
running in the background all the time. He mentioned that it might be 
nice if we could implement a way around this, as he always has to 
manually identify files otherwise.

-Tyler

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