options for #cpu and other?

[Rob Newberry]

When compiling with GCC on Linux/X86, the following will produce a
warning:

	#if #cpu(i386)
		#warning "X86 processor"
	#endif

which is exactly what I want.

Unfortunately, I can't find any information on "#cpu" -- I'm looking for 
other pre-defined options like this.  Are there any others like "#cpu" -- 
"#system" for example?  Is there a mechanism for getting information about 
these from GCC?  Is this documented somewhere?  Sadly, searching google 
for "#cpu" generates absolutely nothing useful...

Thanks a ton!

Rob