Add a feature to use dynamic linkage

[jcjones]

Thank you for maintaining this binding!

It'd be a nice add-on to support dynamic linkage for situations where static isn't doable. In Firefox there's an example doing this with libpulse.so which I'm pretty sure was generated using the dynamic/static dlopen feature support in bindgen. I'll probably run bindgen myself to make a dynamic version, but it'd be great to have in the lib.

If you're interested, I or my team could produce a PR for this, but it'd probably be big and ugly from the code generator.

[ttaubert]

I don't think that bindgen actually supports dynamically loading shared libraries. The pulse-ffi code says it was generated but maybe it was only partially? Maybe only the function signatures when importing it first? The history of the file doesn't make it seems like there's a generator there, which leads me to believe that the "dlopen" feature was added manually.

[anisse]

Nowadays, bindgen supports dynamic loading. Would you be open to have a PR for this ?