[#192] Fix variable redeclarations causing TypeError on 3.24
Created by: elbenfreund
GNOME Shell 3.24 now uses mozjs38 (SpiderMonkey 38) which has stricter syntax rules. https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey
In particular, it errors out on redeclarations of a variable inside of a code block.
This commit addresses this issue by renaming the reused variables to more verbose names to reflect their actual usage rather than to simply avoid the problem by reassigning.
Closes: #191