Use static string with fail!() and remove fail!(fmt!())

fail!() used to require owned strings but can handle static strings
now. Also, it can pass its arguments to fmt!() on its own, no need for
the caller to call fmt!() itself.

src/libsyntax/codemap.rs

@@ -430,8 +430,8 @@ priv impl CodeMap {
             }
         }
         if (a >= len) {
-            fail!(fmt!("position %u does not resolve to a source location",
-                      pos.to_uint()))
+            fail!("position %u does not resolve to a source location",
+                      pos.to_uint())
         }
 
         return a;