Merged from branch 1.7, revisions 3607-3725. Fix some compilation errors, fix soname in Linux Makefile, calculation fix in vector2d class, CGUIScrollBar event handling fix.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@3726 dfc29bdd-3216-0410-991c-e03cc46cb475