Remove by-copy mode from std, mostly

One instance remains in net_tcp due to a foreign fn. Lots of
instances remain in serialization.rs, but IIRC that is being removed.

I had to do unholy things to task-perf-word-count-generic to get it
to compile after demoding pipes. I may well have messed up its
performance, but it passes.

src/libcore/future.rs

@@ -87,7 +87,7 @@ pub fn from_port<A:Send>(port: future_pipe::client::waiting<A>) ->
     }
 }
 
-pub fn from_fn<A>(+f: ~fn() -> A) -> Future<A> {
+pub fn from_fn<A>(f: ~fn() -> A) -> Future<A> {
     /*!
      * Create a future from a function.
      *
@@ -99,7 +99,7 @@ pub fn from_fn<A>(+f: ~fn() -> A) -> Future<A> {
     Future {state: Pending(move f)}
 }
 
-pub fn spawn<A:Send>(+blk: fn~() -> A) -> Future<A> {
+pub fn spawn<A:Send>(blk: fn~() -> A) -> Future<A> {
     /*!
      * Create a future from a unique closure.
      *