Remove unused imports

I was able to remove unused imports, and fix the following warnings

src/libstd/hashmap.rs:23:15: 23:23 warning: unused import [-W unused-imports (default)]
src/libstd/task/spawn.rs:95:15: 95:23 warning: unused import [-W unused-imports (default)]
src/libstd/rt/uv/mod.rs:42:0: 42:9 warning: unused import [-W unused-imports (default)]
src/libstd/rt/uv/mod.rs:45:0: 45:9 warning: unused import [-W unused-imports (default)]
src/librustc/middle/trans/meth.rs:26:0: 26:26 warning: unused import [-W unused-imports (default)]
src/librustc/back/link.rs:210:20: 210:25 warning: unused import [-W unused-imports (default)]

I was unable to fix the following unused import warnings. The code
here was weird.

src/libextra/std.rc:40:11: 40:14 warning: unused import [-W unused-imports (default)]
src/libextra/std.rc:40:16: 40:24 warning: unused import [-W unused-imports (default)]

src/librustc/back/link.rs

@@ -207,7 +207,7 @@ pub mod write {
     use driver::session;
     use lib::llvm::llvm;
     use lib::llvm::{ModuleRef, mk_pass_manager, mk_target_data};
-    use lib::llvm::{False, ContextRef};
+    use lib::llvm::{ContextRef};
     use lib;
 
     use back::passes;

src/librustc/middle/trans/meth.rs

@@ -23,7 +23,6 @@ use middle::trans::common::*;
 use middle::trans::expr::{SaveIn, Ignore};
 use middle::trans::expr;
 use middle::trans::glue;
-use middle::trans::inline;
 use middle::trans::monomorphize;
 use middle::trans::type_of::*;
 use middle::ty;

src/libstd/hashmap.rs

@@ -20,7 +20,7 @@ use cmp::{Eq, Equiv};
 use hash::Hash;
 use old_iter::BaseIter;
 use old_iter;
-use iterator::{Iterator, IteratorUtil};
+use iterator::{IteratorUtil};
 use option::{None, Option, Some};
 use rand::RngUtil;
 use rand;

src/libstd/rt/uv/mod.rs

@@ -39,10 +39,8 @@ use option::*;
 use str::raw::from_c_str;
 use to_str::ToStr;
 use ptr::RawPtr;
-use libc;
 use vec;
 use ptr;
-use cast;
 use str;
 use libc::{c_void, c_int, size_t, malloc, free};
 use cast::transmute;

src/libstd/task/spawn.rs

@@ -92,7 +92,7 @@ use uint;
 use util;
 use unstable::sync::{Exclusive, exclusive};
 use rt::local::Local;
-use iterator::{Iterator, IteratorUtil};
+use iterator::{IteratorUtil};
 
 #[cfg(test)] use task::default_task_opts;
 #[cfg(test)] use comm;