[patch] reduce namespace polloution from sys/ucontext.h on arm

[peter green]

Joseph S. Myers wrote:
> The most obvious users of these definitions would be (native) GDB and 
> gdbserver - do those still build OK (i.e. include the correct headers to 
> get the definitions they need and not rely on any definitions that were 
> removed) after this patch?
>   
I have built the debian gdb package (which builds both gdb and 
gdbserver) sucessfully
on a system with this patch.

> Have you verified that it still works to include both <sys/ucontext.h> and 
> <sys/procfs.h> in the same source file, in either order?
>   
I had already tried that in one order, just tried the other order too. 
Both work fine.

When I copied a structure definition over to remove the dependency I 
made sure
to rename it (following the name used for the equivilent structure on 
amd64).