RFA: Remove ARM syscall support from newlib

[Can Finner]

> Won't this require all users to now use a link script in order to build
> their binaries.  If so, then I think this will break testing of GCC.
>
link script might be unnecessary, but additional libraries in command line.
If this is not an issue, I guess it's better to remove syscalls in newlib,
since it's already different with libgloss, getting more difficult to
keep it sync with libgloss and might cause problem in maintaining and
using it.

Thanks.
-- 
Regards.