Support for Intel-based Macintosh / Darwin 8.1 x86

[Steven Tamm]

I checked in changes to support Emacs on Intel-based Mac OS X 10.4  
and Darwin 8.1.  I tested it at the WWDC lab and it worked perfectly.

However, I couldn't get the PowerPC build I have of Emacs to run  
correctly in Rosetta.  I kept getting a Bus error, and didn't have  
time to do the cross-architecture debugging.  I'd recommend not  
bothering and just recompiling from scratch.  It only takes about 2  
minutes.

A universal binary is not possible right now because of the unexec  
process.  Since you can only unexec by running the application, you  
wouldn't be able to unexec on the opposite platform (since Rosetta  
would munge everything up).  I talked to the guy that did Apple's  
emacs port and he said they created a wrapper application that runs  
unexec the first time you execute the process.  He said it would be  
available once the rest of darwin x86 is published.  I've added a  
todo item to mac/README to possibly include this wrapper back into  
the tree.

-Steven