update release date (first release candidate did fall through)

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code@4609 dfc29bdd-3216-0410-991c-e03cc46cb475
- Added support for texture cube in OpenGL driver.
- Fixed issue related to regenerateMipMapLevels in OpenGL driver.
- Added missing files to VS2012 project.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code@4610 dfc29bdd-3216-0410-991c-e03cc46cb475