Fix build and remove warnings

Author: José Valim

Diff for: lib/elixir/lib/exception.ex

@@ -155,7 +155,6 @@ defmodule Exception do
         { module, function, arity_or_args, location } |
         { function, arity_or_args, location }
 
-  @typep function :: atom
   @typep arity_or_args :: non_neg_integer | list
   @typep location :: Keyword.t
 

Diff for: lib/elixir/lib/version.ex

@@ -140,7 +140,7 @@ defmodule Version do
     case Version.Parser.parse_requirement(requirement) do
       { :ok, _req } ->
         true
-      { :error, reason } ->
+      { :error, _reason } ->
         false
     end
   end