[SDL] RFC: atomic ops

[Antonio SJ Musumeci]

I've got much of it done... for the platforms I'm willing to do. I'm 
wondering though what people are expecting... if anything? Right now 
I've followed GLIBs API. Would people rather have like the Linux 
kernel's more robust API? Haven't done pointers yet... just ints. Would 
people rather see global functions, static inlined header functions, or 
full macro based? Right now I've made it all macros to make sure it's 
inlined... but I'm not sure how portable it is. C99 draft is all I've 
got and it's not entirely clear. But the code works with -ansi and 
-std=c89 on gcc. What kind of default should be fallen back to? GLIB 
uses mutexs but that wont work for shared memory, multiprocess 
applications. Is that alright?