Stroke IME

Add Chinse stroke IME for Firefox OS.
这用只调用一次的函数，直接通过ccall调用，而不用通过cwrap封装成js函数。ccall和cwrap用法详见http://kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html