BackBuffer ALPHA channel doesn't work on Android devices

Hi,

After recent update from Unity 4.1.x to 4.5, I've found quite critical issue with frame buffer on Android devices.

Repro:
1. Set camera clear flags to solid color, as rendering path use Forward.
2. Set the clear color ALPHA channel to something other than default 255, for example set it to 0
3. Everything works on PC, alpha channel is cleared to 0
4. Build an Android build and observe the alpha is cleared to default 255

This did work on Unity 4.1.2 for sure. It's critical because it...

BackBuffer ALPHA channel doesn't work on Android devices