- Improved compressed texture system handling (it avoid code duplicate between all drivers).
- Added ETC1 and ETC2 compressed textures support via PVR loader. (This feature require tests on platform which support ETC1 and ETC2 formats).

git-svn-id: http://svn.code.sf.net/p/irrlicht/code/branches/ogl-es/@4530 dfc29bdd-3216-0410-991c-e03cc46cb475
Added support for PVR loader on iOS platforms. All ETC1, ETC2, PVRTC1 and PVRTC2 formats was checked on dedicated platforms.

git-svn-id: http://svn.code.sf.net/p/irrlicht/code/branches/ogl-es/@4531 dfc29bdd-3216-0410-991c-e03cc46cb475
- Improved texture creation system (it avoid create a texture when image is missing or color format isn't supported).

git-svn-id: http://svn.code.sf.net/p/irrlicht/code/branches/ogl-es/@4532 dfc29bdd-3216-0410-991c-e03cc46cb475
Added support for compressed textures in OpenGL ES1 driver.

git-svn-id: http://svn.code.sf.net/p/irrlicht/code/branches/ogl-es/@4533 dfc29bdd-3216-0410-991c-e03cc46cb475