std: Stabilize the `ffi` module

The two main sub-modules, `c_str` and `os_str`, have now had some time to bake
in the standard library. This commits performs a sweep over the modules adding
various stability tags.

The following APIs are now marked `#[stable]`

* `OsString`
* `OsStr`
* `OsString::from_string`
* `OsString::from_str`
* `OsString::new`
* `OsString::into_string`
* `OsString::push` (renamed from `push_os_str`, added an `AsOsStr` bound)
* various trait implementations for `OsString`
* `OsStr::from_str`
* `OsStr::to_str`
* `OsStr::to_string_lossy`
* `OsStr::to_os_string`
* various trait implementations for `OsStr`
* `CString`
* `CStr`
* `NulError`
* `CString::new` - this API's implementation may change as a result of
  rust-lang/rfcs#912 but the usage of `CString::new(thing)` looks like it is
  unlikely to change. Additionally, the `IntoBytes` bound is also likely to
  change but the set of implementors for the trait will not change (despite the
  trait perhaps being renamed).
* `CString::from_vec_unchecked`
* `CString::as_bytes`
* `CString::as_bytes_with_nul`
* `NulError::nul_position`
* `NulError::into_vec`
* `CStr::from_ptr`
* `CStr::as_ptr`
* `CStr::to_bytes`
* `CStr::to_bytes_with_nul`
* various trait implementations for `CStr`

The following APIs remain `#[unstable]`

* `OsStr*Ext` traits remain unstable as the organization of `os::platform` is
  uncertain still and the traits may change location.
* `AsOsStr` remains unstable as generic conversion traits are likely to be
  rethought soon.

The following APIs were deprecated

* `OsString::push_os_str` is now called `push` and takes `T: AsOsStr` instead (a
  superset of the previous functionality).

2 files changed, 4 insertions, 6 deletions

diff --git a/src/compiletest/compiletest.rs b/src/compiletest/compiletest.rs
index b9e6f1842ee..a5d087b6dd2 100644
--- a/src/compiletest/compiletest.rs
+++ b/src/compiletest/compiletest.rs
@@ -22,7 +22,6 @@
 #![feature(unicode)]
 #![feature(core)]
 #![feature(path)]
-#![feature(os)]
 #![feature(io)]
 #![feature(fs)]
 #![feature(net)]
diff --git a/src/compiletest/runtest.rs b/src/compiletest/runtest.rs
index 7fb1a436ba3..04714b50fc0 100644
--- a/src/compiletest/runtest.rs
+++ b/src/compiletest/runtest.rs
@@ -20,7 +20,6 @@ use procsrv;
 use util::logv;
 
 use std::env;
-use std::ffi::OsStr;
 use std::fmt;
 use std::fs::{self, File};
 use std::io::BufReader;
@@ -1323,7 +1322,7 @@ fn make_exe_name(config: &Config, testfile: &Path) -> PathBuf {
     let mut f = output_base_name(config, testfile);
     if !env::consts::EXE_SUFFIX.is_empty() {
         let mut fname = f.file_name().unwrap().to_os_string();
-        fname.push_os_str(OsStr::from_str(env::consts::EXE_SUFFIX));
+        fname.push(env::consts::EXE_SUFFIX);
         f.set_file_name(&fname);
     }
     f
@@ -1433,7 +1432,7 @@ fn make_out_name(config: &Config, testfile: &Path, extension: &str) -> PathBuf {
 fn aux_output_dir_name(config: &Config, testfile: &Path) -> PathBuf {
     let f = output_base_name(config, testfile);
     let mut fname = f.file_name().unwrap().to_os_string();
-    fname.push_os_str(OsStr::from_str("libaux"));
+    fname.push("libaux");
     f.with_file_name(&fname)
 }
 
@@ -1647,8 +1646,8 @@ fn append_suffix_to_stem(p: &Path, suffix: &str) -> PathBuf {
         p.to_path_buf()
     } else {
         let mut stem = p.file_stem().unwrap().to_os_string();
-        stem.push_os_str(OsStr::from_str("-"));
-        stem.push_os_str(OsStr::from_str(suffix));
+        stem.push("-");
+        stem.push(suffix);
         p.with_file_name(&stem)
     }
 }