Also the case of start/end points being identical now avoids invalid numbers from division by 0 and just returns the start point
Basically it's now the same again as line2d::getClosestPoint (which also got a comment fix)
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6593 dfc29bdd-3216-0410-991c-e03cc46cb475
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