- Changed line2d getVector implementation to match line3d (Was start - end, changed it to end - start).
 - Removed default values for R, G and B for SColorf constructor and added a default constructor that mimics the default values behavior.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2410 dfc29bdd-3216-0410-991c-e03cc46cb475