Linux/macOS dynamic library symbolic links need a rethink

[markfinal]

Having the symbolic links for dynamic libraries as real modules is nice, but a mistake I believe.

From the Linux documentation, these only ever need to be created at install, so these could be moved to the SDK creation part of Publishing.

The SOName of a dynamic library should be optional. As if it's not needed, then you can just link against the full path of the real name of the shared library, and it'll work, but only on your machine. Which is fine for testing.

But for SDK libraries, they should enable the SOname option. Creating the SDK should then generate the SOname symbolic link and the linker name symbolic link.

Linking against the library in the SDK should then link against the linker name symbolic link, and deploy the SOname symbolic link and realname library.

On macOS, we should be able to create a linker name symbolic link at install time.
Not sure about the SO name equivalent. Depends on what we write into the install_name.