Fixed "Texture is not power of two" warning

Decal diffuse texture was generating a warning. Created a new decal
diffuse along with a new normal map. This is a replacement pull request
for previous request #6196.

examples/textures/decal/LICENSE.TXT

@@ -0,0 +1,5 @@
+decal-diffuse.png
+decal-normal.jpg
+
+Licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication License:
+http://creativecommons.org/publicdomain/zero/1.0/