Make hoymiles library usable for other architectures

[greenflash1986]

Hi @tbnobody first of all thanks for the great work.

After I were unable to log my supply from my inverter with the Voltcraft plug, I stumpled accross the thread on Mikrocontroller. The work done there is very appreciated and although I'm unable to remember all the posts I where able to find the two repositories.

Now I want to use my spare Atmega328PB for the logging and I found your repository with the library approach the most promising. Although I don't know if the Atmega has enough speed or RAM (currently the Atmega-branch with only a simple main builds with >4kb and the Atmega only has 2kb) I already did some things to make the hoymiles library compile for the atmelavr-toolchain.

This PR is a request for comments: it's an idea to make things working for multiple platforms and maybe you want to change the library code in such a manner. I'm a software developer but my embedded skills and C++ knowledge is very limited. Therefore I would not assume that my code is correct in all details. Please have a look and feel free to comment.

Best regards GreenFlash1986

[greenflash1986]

Updated base to current master.

Best regards