Various typo fixes - only in comments, no code changes.
Merge branch 'Marlin_v1' of https://github.com/ErikZalm/Marlin into typofixes_upstream
Merge branch 'Marlin_v1' of https://github.com/ErikZalm/Marlin into typofixes_upstream
Merge branch 'Marlin_v1' of https://github.com/ErikZalm/Marlin into typofixes_upstream
Merge branch 'Marlin_v1' of https://github.com/ErikZalm/Marlin into typofixes_upstream
Merge pull request #781 from Cylindric3D/typofixes_upstream

Various typo fixes #3 - only in comments, no code changes.