Runtime arch specific

[Hien Nguyen]

Hi Martin,

Ananth discussed with me about the possibility of splitting the runtime 
arch specific code. Currently only a few files (stack.c, copy.c, 
current.c and regs.h) contain arch specific code. How about organize the 
runtime somewhat similar to the kernel

arch/i386/stack.c
arch/i386/current.c
arch/i386/copy.c
include/arch/i386/regs.h

and so on...

There are couple advantages such as
1. Porting the runtime to another arch one can quickly look at the code 
under arch.
2. When people modifying on arch are ware of the other arch have to also 
be changed.

Regards, Hien.