std: Add a new `env` module

This is an implementation of [RFC 578][rfc] which adds a new `std::env` module
to replace most of the functionality in the current `std::os` module. More
details can be found in the RFC itself, but as a summary the following methods
have all been deprecated:

[rfc]: https://github.com/rust-lang/rfcs/pull/578

* `os::args_as_bytes`   => `env::args`
* `os::args`            => `env::args`
* `os::consts`          => `env::consts`
* `os::dll_filename`    => no replacement, use `env::consts` directly
* `os::page_size`       => `env::page_size`
* `os::make_absolute`   => use `env::current_dir` + `join` instead
* `os::getcwd`          => `env::current_dir`
* `os::change_dir`      => `env::set_current_dir`
* `os::homedir`         => `env::home_dir`
* `os::tmpdir`          => `env::temp_dir`
* `os::join_paths`      => `env::join_paths`
* `os::split_paths`     => `env::split_paths`
* `os::self_exe_name`   => `env::current_exe`
* `os::self_exe_path`   => use `env::current_exe` + `pop`
* `os::set_exit_status` => `env::set_exit_status`
* `os::get_exit_status` => `env::get_exit_status`
* `os::env`             => `env::vars`
* `os::env_as_bytes`    => `env::vars`
* `os::getenv`          => `env::var` or `env::var_string`
* `os::getenv_as_bytes` => `env::var`
* `os::setenv`          => `env::set_var`
* `os::unsetenv`        => `env::remove_var`

Many function signatures have also been tweaked for various purposes, but the
main changes were:

* `Vec`-returning APIs now all return iterators instead
* All APIs are now centered around `OsString` instead of `Vec<u8>` or `String`.
  There is currently on convenience API, `env::var_string`, which can be used to
  get the value of an environment variable as a unicode `String`.

All old APIs are `#[deprecated]` in-place and will remain for some time to allow
for migrations. The semantics of the APIs have been tweaked slightly with regard
to dealing with invalid unicode (panic instead of replacement).

The new `std::env` module is all contained within the `env` feature, so crates
must add the following to access the new APIs:

    #![feature(env)]

[breaking-change]

1 files changed, 6 insertions, 5 deletions

diff --git a/src/compiletest/compiletest.rs b/src/compiletest/compiletest.rs
index b73623223fd..7c0ee7be8a4 100644
--- a/src/compiletest/compiletest.rs
+++ b/src/compiletest/compiletest.rs
@@ -22,6 +22,7 @@
 #![feature(std_misc)]
 #![feature(test)]
 #![feature(unicode)]
+#![feature(env)]
 
 #![deny(warnings)]
 
@@ -31,7 +32,7 @@ extern crate getopts;
 #[macro_use]
 extern crate log;
 
-use std::os;
+use std::env;
 use std::old_io;
 use std::old_io::fs;
 use std::thunk::Thunk;
@@ -48,7 +49,7 @@ pub mod common;
 pub mod errors;
 
 pub fn main() {
-    let args = os::args();
+    let args = env::args().map(|s| s.into_string().unwrap()).collect();;
     let config = parse_config(args);
 
     if config.valgrind_path.is_none() && config.force_valgrind {
@@ -224,7 +225,7 @@ pub fn run_tests(config: &Config) {
         //arm-linux-androideabi debug-info test uses remote debugger
         //so, we test 1 task at once.
         // also trying to isolate problems with adb_run_wrapper.sh ilooping
-        os::setenv("RUST_TEST_TASKS","1");
+        env::set_var("RUST_TEST_TASKS","1");
     }
 
     match config.mode {
@@ -232,7 +233,7 @@ pub fn run_tests(config: &Config) {
             // Some older versions of LLDB seem to have problems with multiple
             // instances running in parallel, so only run one test task at a
             // time.
-            os::setenv("RUST_TEST_TASKS", "1");
+            env::set_var("RUST_TEST_TASKS", "1");
         }
         _ => { /* proceed */ }
     }
@@ -245,7 +246,7 @@ pub fn run_tests(config: &Config) {
     old_io::test::raise_fd_limit();
     // Prevent issue #21352 UAC blocking .exe containing 'patch' etc. on Windows
     // If #11207 is resolved (adding manifest to .exe) this becomes unnecessary
-    os::setenv("__COMPAT_LAYER", "RunAsInvoker");
+    env::set_var("__COMPAT_LAYER", "RunAsInvoker");
     let res = test::run_tests_console(&opts, tests.into_iter().collect());
     match res {
         Ok(true) => {}