Add newlib floorf

Author: tesuji

src/math/floorf.rs

@@ -18,13 +18,13 @@ const HUGE: f32 = 1.0e30;
 /// Return x rounded toward -inf to integral value
 #[inline]
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
-pub fn floorf(x: f32) -> f32 {
+pub extern "C" fn floorf(x: f32) -> f32 {
     // On wasm32 we know that LLVM's intrinsic will compile to an optimized
     // `f32.floor` native instruction, so we can leverage this for both code size
     // and speed.
     llvm_intrinsically_optimized! {
         #[cfg(target_arch = "wasm32")] {
-            return unsafe { ::core::intrinsics::floorf32(x) }
+            return unsafe { core::intrinsics::floorf32(x) }
         }
     }