TRAC #11316.
Keep a dirty data flag, recreate the texture when it is set.
Texture now owns getTexture() and calls a virtual
createTexture method when the derived classes need to recreate.

Signed-off-by: Daniel Koch

Author:    Andrew Lewycky <andrew.lewycky@transgaming.com>

git-svn-id: https://angleproject.googlecode.com/svn/trunk@12 736b8ea6-26fd-11df-bfd4-992fa37f6226