Set FBO size to 512x512 when framebuffer changed only

Hopefully it fixes most of the texture sizing issues .Tested against all the following games and renders correctly so far. 

1. Danganronpa ( with FramebuffersToMem = True) #2694
![screen00000](https://f.cloud.github.com/assets/3000282/768063/2b542bc0-e895-11e2-8c0d-14468614a215.png)
This is the log and we can see no more oversizing FBO 
52:45:454 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 00088000 : 480 x 272 x 3
52:45:454 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 00000000 : 480 x 272 x 3
52:45:454 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 00154000 : 128 x 72 x 1


2. FF Crisis Core #2693
![screen00002](https://f.cloud.github.com/assets/3000282/768076/8acba2e0-e895-11e2-9d4c-c32436dc536c.png)
05:47:989 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 00088000 : 480 x 272 x 3
05:47:989 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 00000000 : 480 x 272 x 3
05:47:989 GLES\Framebuffer.cpp:1187 I[HLE]: Destroying FBO for 04154000 : 64 x 64 x 2

3. Final Fantasy Type-0
4. Castlevania The Dracula X Chronicles
5. Gundam AGE Universe
6. God of War Chains of Olympus
7. Saint Seiya Omega
8. MotoGP
9. Yu-Gi-Oh! 5D's Tag Force 6
10.Last_Ranker