Bump to 0.4.0

[bvssvni]

Currently the libc is updated in the Cargo.toml but not yet published. When publishing, it is a good idea to bump the first non-zero number to avoid breaking existing code downstream.

[huonw]

Why is this necessary? As far as I know rand doesn't expose anything from libc directly so it shouldn't be a breaking changing to use a higher version of libc.

[bvssvni]

@huonw You're right.

[bvssvni]

It seems the changes since 0.3.11 are non-breaking, so it is possible that bumping to 0.3.12 won't break downstream crates.

[bvssvni]

rand depends on winapi, which depends on kernel32-sys. Since winapi uses a "*" version of kernel32-sys, it means that everything breaks anyway. Might as well just bump it 0.3.12. See retep998/winapi-rs#238

[retep998]

Since winapi uses a "*" version of kernel32-sys

winapi only dev depends on the -sys crates, so it doesn't apply to downstream consumers.

[bvssvni]

@retep998 Right. My mistake.