Start using core::path2::Path in a lot of places.

src/compiletest/errors.rs

@@ -6,7 +6,7 @@ export expected_error;
 type expected_error = { line: uint, kind: ~str, msg: ~str };
 
 // Load any test directives embedded in the file
-fn load_errors(testfile: ~str) -> ~[expected_error] {
+fn load_errors(testfile: &Path) -> ~[expected_error] {
     let mut error_patterns = ~[];
     let rdr = result::get(io::file_reader(testfile));
     let mut line_num = 1u;