Further enhance compare_split_screen_popup()

Since compare_split_screen_popup() looks like it's been patched repeatedly, and since a display I want to work on uses that function, I don't feel to bad about adding (and documenting!) another kludgey feature to the function to allow for the change I want to make later on.
Add colored hinting to the item exam sidebar

When examining an item, the sidebar listing possible actions now has colored hinting.

Green: can do that action
Red: the item permits that action, but circumstances don't
Gray: the item does not permit that action

A few things (notably, Unload) don't hint yet. Also, there may be some rare cases that were missed.
Should probably add myself to the credits at this point
Add hinting to "U"nload as well
Add a "D"isassemble option to the item examination screen
Make room for the word "Disassemble"

Looks like that sidebar I was playing with cut off the last letter of "disassemble".
Three options: move everything one character to the left; widen the window; or choose a shorter word.
I went with the first of those options, since it's unlikely to break anything, still uses the right word, and there was room.
Remove an unused function declaration, and fix comment alignment
Rename the use_rating enum to hint_rating
Merge pull request #291 from ethankaminski/examine_hinting

Improve item examination sidebar