Bug 1445117 - Remove duplicates from nsGkAtoms. r=froydnj

In each case, the atom had an obvious name and a weird name. Where possible, I
kept the obvious name and commented out the weird name, viz:

- `mixed` over `_mixed` for "mixed"
- `el` over `el_` for "el"
- `other` over `other_` for "other"
- `remote` over `Remote` for "remote"

But for several of them I didn't do that, because the weird name is used
within the HTML5 parser -- which is a huge pain to modify because it involves
code generated by code from another repo -- so I kept the weird name and
commented out the obvious name, viz:

- `list_` over `list` for "list"
- `svgSwitch` over `_switch` for "switch"
- `set_` over `set` for "set"

MozReview-Commit-ID: Jp3CpdWXNDm

accessible/html/HTMLFormControlAccessible.cpp

@@ -406,7 +406,7 @@ HTMLTextFieldAccessible::NativeState()
   }
 
   // Expose autocomplete state if it has associated autocomplete list.
-  if (mContent->AsElement()->HasAttr(kNameSpaceID_None, nsGkAtoms::list))
+  if (mContent->AsElement()->HasAttr(kNameSpaceID_None, nsGkAtoms::list_))
     return state | states::SUPPORTS_AUTOCOMPLETION | states::HASPOPUP;
 
   // Ordinal XUL textboxes don't support autocomplete.