Added STL mesh file format reader and writer. This is a pretty simple format, but I wanted to try the mesh writer interface.
git-svn-id: http://svn.code.sf.net/p/irrlicht/code/trunk@983 dfc29bdd-3216-0410-991c-e03cc46cb475
Added IGUIElement::isMyChild, isPointInside, SEvent.GUIEvent.Element.
Changed setFocus and removeFocus to return bools.
changed quaternion::toAngleAxis to use iszero.
git-svn-id: http://svn.code.sf.net/p/irrlicht/code/trunk@763 dfc29bdd-3216-0410-991c-e03cc46cb475