std: Move the cmath module into the sys module

This commit moves the `f32::cmath` and `f64::cmath` modules into the
`sys` module. Note that these are not publicly exported modules, simply
implementation details. These modules are already platform-specific with
shims on MSVC and this is mostly just a reflection of that reality. This
should also help cut down on `#[cfg]` traffic if platforms are brought on
which don't directly support these functions.

src/libstd/sys/unix/cmath.rs

@@ -0,0 +1,43 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![cfg(not(test))]
+
+use libc::{c_float, c_double};
+
+#[link_name = "m"]
+extern {
+    pub fn acos(n: c_double) -> c_double;
+    pub fn acosf(n: c_float) -> c_float;
+    pub fn asin(n: c_double) -> c_double;
+    pub fn asinf(n: c_float) -> c_float;
+    pub fn atan(n: c_double) -> c_double;
+    pub fn atan2(a: c_double, b: c_double) -> c_double;
+    pub fn atan2f(a: c_float, b: c_float) -> c_float;
+    pub fn atanf(n: c_float) -> c_float;
+    pub fn cbrt(n: c_double) -> c_double;
+    pub fn cbrtf(n: c_float) -> c_float;
+    pub fn cosh(n: c_double) -> c_double;
+    pub fn coshf(n: c_float) -> c_float;
+    pub fn expm1(n: c_double) -> c_double;
+    pub fn expm1f(n: c_float) -> c_float;
+    pub fn fdim(a: c_double, b: c_double) -> c_double;
+    pub fn fdimf(a: c_float, b: c_float) -> c_float;
+    pub fn hypot(x: c_double, y: c_double) -> c_double;
+    pub fn hypotf(x: c_float, y: c_float) -> c_float;
+    pub fn log1p(n: c_double) -> c_double;
+    pub fn log1pf(n: c_float) -> c_float;
+    pub fn sinh(n: c_double) -> c_double;
+    pub fn sinhf(n: c_float) -> c_float;
+    pub fn tan(n: c_double) -> c_double;
+    pub fn tanf(n: c_float) -> c_float;
+    pub fn tanh(n: c_double) -> c_double;
+    pub fn tanhf(n: c_float) -> c_float;
+}

src/libstd/sys/unix/mod.rs

@@ -38,6 +38,7 @@ pub mod args;
 pub mod android;
 #[cfg(feature = "backtrace")]
 pub mod backtrace;
+pub mod cmath;
 pub mod condvar;
 pub mod env;
 pub mod ext;