Same as the corresponding change in Corrade, this allows each function
to explicitly specify its dependencies, making it no longer depending on
what a particular Emscripten version decides to include by default, or
forcing users to painstakingly fill the EXPORTED_FUNCTIONS array when
linking the final executable.
It also allows the code to eventually get conditionally included or not
with preprocessor branches, for example to not include environment
queries for code that won't ever access Node.js console.
Vladimír Vondruš