Use __EMSCRIPTEN__ and not EMSCRIPTEN.
Use __EMSCRIPTEN__ and not EMSCRIPTEN.

We prefer to use __EMSCRIPTEN__ as the preprocessor flag for detecting
emscripten.

WebAssembly/polyfill-prototype-1,WebAssembly/polyfill-prototype-1,WebAssembly/polyfill-prototype-1,WebAssembly/polyfill-prototype-1,WebAssembly/polyfill-prototype-1