libstd: turn time::Tm and time::Timespec into structs

This avoids rust-lang#4044 by not using the enum wrapper, and turning Tm_
directly into a struct. Along the way it modernizes the codebase
to eliminate no-implicit-copies warnings.

Author: erickt

Diff for: src/librustc/middle/trans/base.rs

@@ -1643,7 +1643,7 @@ fn trans_fn(ccx: @crate_ctxt,
             impl_id: Option<ast::def_id>) {
     let do_time = ccx.sess.trans_stats();
     let start = if do_time { time::get_time() }
-                else { {sec: 0i64, nsec: 0i32} };
+                else { time::Timespec::new(0, 0) };
     debug!("trans_fn(ty_self=%?)", ty_self);
     let _icx = ccx.insn_ctxt("trans_fn");
     ccx.stats.n_fns += 1;

Diff for: src/libstd/std.rs

@@ -0,0 +1,7 @@
+// A curious inner-module that's not exported that contains the binding
+// 'std' so that macro-expanded references to std::serialization and such
+// can be resolved within libcore.
+#[doc(hidden)] // FIXME #3538
+mod std {
+    pub use serialization;
+}