Usually something like __IRR_SOME_GUARD_INCLUDED__ replaced by IRR_SOME_GUARD_INCLUDED.
Removing underscores at the end wasn't necessary, but more symmetric (probably the reason they got added there as well).
While this touches every header it shouldn't affect users (I hope).
Also a few whitespace changes to unify whitespace usage a bit.
And a bunch of spelling fixes in comments.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6252 dfc29bdd-3216-0410-991c-e03cc46cb475
