Issue building on Ubuntu 19.04

[jakew009]

Hey

Thanks so much for creating and releasing this!

I had an issue building it on Ubuntu 19.04 with OpenVPN so I thought I would share them here in case anyone else had the same troubles

When I called make plugin, I was getting an error that openvpn-plugin.h could not be found.
On some further investigation, I found that by changing line 21 from:

#include <openvpn-plugin.h>
to:
#include <openvpn/openvpn-plugin.h>

It was able to build and work perfectly.

My linux knowledge is fairly limited so I don't know what a proper fix for this would be :)

[wbwork]

Applies also for Ubuntu 18.04 already.