Make EGL function eglCreateContext spec-conformant and actually read the EGL_CONTEXT_CLIENT_VERSION field when creating a context. Require the version number 2, since WebGL1 maps to GLES2.
Move emscripten-source-map.min.js to src/ since it is a non-tests file needed by public use when user wants to emscripten_log with a C callstack. Remove redundant emscripten_demangle function.