Add test showcasing lifetime issue of AsUniformValue for Texture2d
Add test showcasing lifetime issue of AsUniformValue for Texture2d

Currently this fails to compile with:
```
error[E0515]: cannot return value referencing function parameter `texture`
   --> tests/texture_creation.rs:103:9
    |
103 |         texture.as_uniform_value()
    |         -------^^^^^^^^^^^^^^^^^^^
    |         |
    |         returns a value referencing data owned by the current function
    |         `texture` is borrowed here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0515`.
```

glium/glium