s/import/use/g; fix class method syntax

appkit.rs

@@ -1,4 +1,4 @@
-import base::objc;
+use base::objc;
 
 #[nolink]
 #[link_args="-framework AppKit"]

cg.rs

@@ -1,6 +1,6 @@
 // FIXME: Should be bindgenned
 
-import libc::{c_void, c_char, size_t};
+use libc::{c_void, c_char, size_t};
 
 #[nolink]
 extern mod cg {

foundation.rs

@@ -1,4 +1,4 @@
-import base::objc;
+use base::objc;
 
 #[nolink]
 #[link_args="-framework Foundation"]