Replace an instance std with core in wasm.rs, such that `#[no_s…

…td]` and the `wasm32` target can be used concurrently.

src/imp/wasm.rs

@@ -143,7 +143,7 @@ mod imp {
 
  #[inline(always)]
  fn reduce_add(v: v128) -> u32 {
- let arr: [u32; 4] = unsafe { std::mem::transmute(v) };
+ let arr: [u32; 4] = unsafe { core::mem::transmute(v) };
  let mut sum = 0u32;
  for val in arr {
  sum = sum.wrapping_add(val);