Fix typos in comments

I fixed some spelling errors using codespell.py from https://github.com/lucasdemarchi/codespell then I manually checked the modified files and committed only the changes inside comments (as you can see from the colored diff most lines have only one letter changed).

I excluded the following files because they had false positives, or they were data files, or they were created outside of OpenLayers:
examples/animator.js
examples/georss.xml
examples/kml/sundials.kml
examples/utfgrid/geography-class/2/1/1.grid.json
lib/OpenLayers/Format/GeoRSS.js
lib/OpenLayers/Lang/*
tools/BeautifulSoup.py

I also excluded the tests directory because I'm not familiar with the tests.