It appears that most of our non-C++/Lua source files are using spaces for
indentation, (except Makefile.am). Added rules to accommodate that, and fix
wrong indentation in Changelog.txt when using github editor.
This is used by github when displaying code in browser
E.g. this fixes a very long standing issue when glancing through code on
gitub, be that for review or online source files: they insist on 8 char tabs,
while we use tabs with width 4.
This can also be used by any self-respecting editor (read: Emacs), but also by
lesser ones (read: vim), and the rest (atom, geany, netbeans, eclipse, xcode,
sublime, textmate, visual studio, etc.)
See http://editorconfig.org/ for full list, and more.
Karl F