Blender Git Loki

GL_TEXTURE_2D_ARRAY wasn't handled in GPU_texture_update

Although the problem was exposed in 9457715d9a6f, the problem was in the
original code that was copied over. To have:

```
} else { /* EXPECTED_VALUE */
```

Without an BLI_assert(value == EXPECTED_VALUE); is asking for troubles.
Yet another reason to favour switch statements with:

```
default:
BLI_assert(!"value not implemented or supported");
```

Instead of chained if/else if/else /* expected_value */.