bug#4298: .egg files could open in archive-mode by default

[Gareth Rees]

Python modules are often distributed as files with the extension  
".egg". These are just ZIP files with a convention about the layout of  
the contents, as described in [1].

It would be nice if Emacs could open these files in archive-mode by  
default, either by adding an entry for the file extension ".egg" to  
auto-mode-alist, or by adding a suitable pattern for ZIP files to  
magic-fallback-mode-alist.

(Perhaps this suggestion will become moot when libmagic is integrated  
into Emacs.)

[1] "The Internal Structure of Python Eggs"; 
http://svn.python.org/projects/sandbox/trunk/setuptools/doc/formats.txt

--
Gareth Rees