rustc: Fix a number of stability lint holes

There are a number of holes that the stability lint did not previously cover,
including:

* Types
* Bounds on type parameters on functions and impls
* Where clauses
* Imports
* Patterns (structs and enums)

These holes have all been fixed by overriding the `visit_path` function on the
AST visitor instead of a few specialized cases. This change also necessitated a
few stability changes:

* The `collections::fmt` module is now stable (it was already supposed to be).
* The `thread_local::imp::Key` type is now stable (it was already supposed to
  be).
* The `std::rt::{begin_unwind, begin_unwind_fmt}` functions are now stable.
  These are required via the `panic!` macro.
* The `std::old_io::stdio::{println, println_args}` functions are now stable.
  These are required by the `print!` and `println!` macros.
* The `ops::{FnOnce, FnMut, Fn}` traits are now `#[stable]`. This is required to
  make bounds with these traits stable. Note that manual implementations of
  these traits are still gated by default, this stability only allows bounds
  such as `F: FnOnce()`.

Additionally, the compiler now has special logic to ignore its own generated
`__test` module for the `--test` harness in terms of stability.

Closes #8962
Closes #16360
Closes #20327

[breaking-change]

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index 526b5edd4cb..b37f5f7a974 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -317,6 +317,7 @@ pub unsafe fn pipe() -> IoResult<Pipe> {
 #[cfg(not(target_os="ios"))]
 #[deprecated(since = "1.0.0", reason = "this function will be removed, use the constants directly")]
 #[unstable(feature = "os")]
+#[allow(deprecated)]
 pub fn dll_filename(base: &str) -> String {
     format!("{}{}{}", consts::DLL_PREFIX, base, consts::DLL_SUFFIX)
 }