Simplify has_top_right() and has_bottom_left().
Simplify has_top_right() and has_bottom_left().

- More meaningful variable names
- Comments to make code more readable.
- Variables declared near use etc.

Change-Id: I1a87d52a73aeefbaee4b9190861155dfcf05985c

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom