Add bindings for ldexp/ldexpf

Should help in fixing wasmerio/wasmer#407

Author: alexcrichton

src/math/ldexp.rs

@@ -0,0 +1,5 @@
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn ldexp(x: f64, n: i32) -> f64 {
+    super::scalbn(x, n)
+}

src/math/ldexpf.rs

@@ -0,0 +1,5 @@
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn ldexpf(x: f32, n: i32) -> f32 {
+    super::scalbnf(x, n)
+}

src/math/mod.rs

@@ -104,6 +104,8 @@ mod fmod;
 mod fmodf;
 mod hypot;
 mod hypotf;
+mod ldexp;
+mod ldexpf;
 mod log;
 mod log10;
 mod log10f;
@@ -166,6 +168,8 @@ pub use self::fmod::fmod;
 pub use self::fmodf::fmodf;
 pub use self::hypot::hypot;
 pub use self::hypotf::hypotf;
+pub use self::ldexp::ldexp;
+pub use self::ldexpf::ldexpf;
 pub use self::log::log;
 pub use self::log10::log10;
 pub use self::log10f::log10f;