Steps to reproduce:
1. Start a new project
2. Add a quad to the scene
3. Create a particles/alpha blended material
4. Assign a texture, set the alpha value to 255
5. Assign the material to the quad and look at the sun through the game object
6. Notice that the sun is inverted

Expected result: Alpha Blended shader should not invert the colors of other blended objects if the alpha value is higher than ~127

Reproduced in: 2018.1.0a7, 2017.3.0f2, 2017.2.0p4, 2017.1.2p4, 5.6.4p4, 5.6.0a1
Not reproduced in: 5.5.5p2, 5.4.6f3
Regression since: 5.6.0a1