This feature was not useful for Cargo users, since Cargo does not give you
the kind of fine-grained control over C library linkage that you need. So
it was just unnecessarily confusing and would cause the build to break if
you enabled it accidentally, say, with --all-features.
This is configurable in upstream now.
Fixes#214.
So far, this just sets it to `4`. It's tempting to set it to `2` when `lowmemory` is enabled
but `lowmemory` is about RAM and not about binary size. This is better addressed by
a resolution of #193.
libsecp256k1 really only barely uses libc at all, and in practice,
things like memcpy/memcmp get optimized into something other than a
libc call. Thus, if we provide simple stub headers, things seem to
work with wasm-pack just fine.
Andrew Poelstra
Tibo-lg
Matt Corallo
Tim Ruffing
Elichai Turkel
Steven Roose