added missing function in emscripten export (#593)
added missing function in emscripten export (#593)

* added missing emscripten export

* added one more function

WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype