Remove unused PostRender method, wich was used by the old ogl-es2 driver.

git-svn-id: http://irrlicht.svn.sourceforge.net/svnroot/irrlicht/branches/ogl-es/@4504 dfc29bdd-3216-0410-991c-e03cc46cb475
Remove unused shader callback methods onsetattributes and onunsetattributes.

git-svn-id: http://irrlicht.svn.sourceforge.net/svnroot/irrlicht/branches/ogl-es/@4505 dfc29bdd-3216-0410-991c-e03cc46cb475
- Fixed OGL ES2.x issues related to last updates of branch.
- Added OGL ES 1.x and 2.x drivers to VS2012 project.

git-svn-id: http://irrlicht.svn.sourceforge.net/svnroot/irrlicht/branches/ogl-es/@4506 dfc29bdd-3216-0410-991c-e03cc46cb475