macros: Move the wrapping macro in a separate file

Will be reused.

src/cuda/device.rs

@@ -8,16 +8,6 @@ pub struct CuDevice {
     device: CUdevice,
 }
 
-macro_rules! wrap {
-    ($val:ident, $res:ident) => (
-        if $res == CUDA_SUCCESS {
-            Ok($val)
-        } else {
-            Err($res)
-        }
-    )
-}
-
 impl CuDevice {
     pub fn new(ordinal: c_int) -> Result<CuDevice, CUresult> {
         let mut d = CuDevice { device: 0 };

src/lib.rs

@@ -1,3 +1,6 @@
 extern crate nvidia_video_codec_sys as ffi;
 
+#[macro_use]
+mod macros;
+
 pub mod cuda;

src/macros.rs

@@ -0,0 +1,11 @@
+macro_rules! wrap {
+    ($val:ident, $res:ident) => (
+        if $res == CUDA_SUCCESS {
+            Ok($val)
+        } else {
+            Err($res)
+        }
+    )
+}
+
+