Add generic export of os symbols

[jnqnfe]

I'm using libloading in a work-in-progress large project; there's a part of the project's design which necessitates returning a raw os symbol. Unfortunately your library currently forces me to write the following:

#[cfg(not(windows))]
use libloading::os::unix::Symbol as LibSymbol;
#[cfg(windows)]
use libloading::os::windows::Symbol as LibSymbol;

Which is messier than I'd like. Could you please add a generic export of os symbols (i.e. ::os::raw::*) to provide a cleaner import of the os symbols, just like std does. Thanks :)

[nagisa]

The current scheme actually mimics the libstd behaviour fairly closely and in your code example achieves the intended purpose – to make platform specific dependencies very visible – fairly well.

A better example from libstd similar to the Symbol case would be RawFd vs RawHandle.

[nagisa]

I'm going to close this out as I believe re-exporting the OS-specific API at a common path would be a mistake at this time. If we ever end up getting an implementation of something like the portability lint the approach on how the APIs are designed would change, but the change would affect significantly more than just this API.