Bug when linking with both move-api and ref-api

[cedricchevalier19]

Alien provides two API move and ref. However they are not compatible.
Linking with both at the same time results in weird behavior. For example, objects are defined in both libraries and their dtors can collide.

To solve this, we can either:

1. Find a way to forbid linking with both libraries at the same time;
2. Putting APIs in their own namespace.

The first solution forbids an user to exploit both APIs which may be interesting on a large code.

[cedricchevalier19]

New user with this bug. We must solve this quickly.