Correct spelling mistakes found by codespell. Fixes lathiat/avahi #167

[warmsocks]

Fixes issue #167.

[EskoDijk]

Good spelling contributions in here. Needs to be changed for the following:

• don't fix typos in variable names that are (potentially) used to provide an external API to Avahi. Changing would break the binding/interface. Best do this in separate PRs where impact can be considered. See separate comments on code lines.
• don't fix typos in 'specs' folder - these are verbatim included IETF specs.

[pemensik]

I have rebase it to current master, which fixed some places. Reverted the specs fixes and added backward compatible definition. @EskoDijk, what do you think about modified version?

[EskoDijk]

@pemensik Thanks, good backward compatible solution in the C code.
However there is still a change in the API for C# code (consists of the two changes in the avahi-sharp directory). The enum item name is changed there in C# which causes any build using this library to break.
(C# doesn't have #define to fix that for us - although there are some tricks maybe to make it work see https://stackoverflow.com/questions/8043027/non-unique-enum-values )

So I would not include this C# change as part of a "typo fix clean sweep PR" like this one.

[EskoDijk]

@pemensik Thanks, that solves it.