Revert "tabs instead of 4 spaces"

This reverts commit 28c9f547bf3f9defc16eafb27b206d5306d78d13.
Revert "Fixed issue https://github.com/mootools/mootools-core/issues/2500"

This reverts commit f1d20ecfa4f3212f49f9374eec579dceb911c537.