Structure for FreeBSD preserving backwards compatibility

[kplindegaard]

An attempt to automatically detect OS and choose the right adaptations as implemented in a subclass called SMBusFreeBSD.

Design criteria:

1. FreeBSD adaptations and adjustments should be fully separate from the Linux implementation. It is quite different, and the Linux implementation must not be full of ifs everywhere.
2. It should be possible to use with SMBus(<busno>) as bus: as before without thinking about OS. This is the preferred usage pattern and just has to work.

Current concerns:

• It's not 100% backwards compatible... :/
• Penalty checking architecture every time a new bus class is instantiated.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

No Coverage information
0.0% Duplication

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[kplindegaard]

PR #151 is expected to be merged into this to handle improved initialization and preservation of the API, meaning that current description will be outdated and hence should be updated when that PR is merged.