move architecture specifics into arch directory

src/arch/mod.rs

@@ -0,0 +1,7 @@
+// Copyright (c) 2015, edef <edef@edef.eu>
+// See the LICENSE file included in this distribution.
+pub use self::imp::Registers;
+
+#[cfg(target_arch = "x86_64")]
+#[path = "x86_64/mod.rs"]
+mod imp;

src/lib.rs

@@ -23,7 +23,6 @@ pub mod stack;
 
 mod debug;
 
-#[cfg(target_arch = "x86_64")]
 mod arch;
 
 #[cfg(feature = "os")]