syntax and rustc: fix some warnings

Author: erickt

src/librustc/back/rpath.rs

@@ -14,7 +14,7 @@ use metadata::cstore;
 use metadata::filesearch;
 
 use std::hashmap::HashSet;
-use std::{num, os, path, uint, util, vec};
+use std::{os, util, vec};
 
 fn not_win32(os: session::os) -> bool {
   os != session::os_win32

src/librustc/metadata/filesearch.rs

@@ -11,7 +11,6 @@
 
 use std::option;
 use std::os;
-use std::{result, str};
 use std::hashmap::HashSet;
 
 // A module for searching for libraries

src/libsyntax/ext/ifmt.rs

@@ -685,7 +685,7 @@ pub fn expand_syntax_ext(ecx: @ExtCtxt, sp: span,
     };
     cx.fmtsp = efmt.span;
     let fmt = expr_to_str(ecx, efmt,
-                          ~"first argument to ifmt! must be a string literal.");
+                          "first argument to ifmt! must be a string literal.");
 
     let mut err = false;
     do parse::parse_error::cond.trap(|m| {