path2: Replace the path module outright

Remove the old path.
Rename path2 to path.
Update all clients for the new path.

Also make some miscellaneous changes to the Path APIs to help the
adoption process.

src/test/bench/core-std.rs

@@ -73,8 +73,8 @@ fn read_line() {
     use std::rt::io::file::FileInfo;
     use std::rt::io::buffered::BufferedReader;
 
-    let path = Path(env!("CFG_SRC_DIR"))
-        .push_rel(&Path("src/test/bench/shootout-k-nucleotide.data"));
+    let path = Path::from_str(env!("CFG_SRC_DIR"))
+        .join_str("src/test/bench/shootout-k-nucleotide.data");
 
     for _ in range(0, 3) {
         let mut reader = BufferedReader::new(path.open_reader(Open).unwrap());

src/test/bench/shootout-fasta.rs

@@ -122,7 +122,7 @@ fn main() {
     };
 
     let writer = if os::getenv("RUST_BENCH").is_some() {
-        io::file_writer(&Path("./shootout-fasta.data"),
+        io::file_writer(&Path::from_str("./shootout-fasta.data"),
                         [io::Truncate, io::Create]).unwrap()
     } else {
         io::stdout()

src/test/bench/shootout-k-nucleotide-pipes.rs

@@ -164,8 +164,8 @@ fn main() {
     let rdr = if os::getenv("RUST_BENCH").is_some() {
         // FIXME: Using this compile-time env variable is a crummy way to
         // get to this massive data set, but include_bin! chokes on it (#2598)
-        let path = Path(env!("CFG_SRC_DIR"))
-            .push_rel(&Path("src/test/bench/shootout-k-nucleotide.data"));
+        let path = Path::from_str(env!("CFG_SRC_DIR"))
+            .join_str("src/test/bench/shootout-k-nucleotide.data");
         ~path.open_reader(Open).unwrap() as ~Reader
     } else {
         ~stdio::stdin() as ~Reader