Rich diffs

[bates64]

With asm-differ's new JSON output format, we can implement a richer diff interface that just the highlighted text we have right now.

• [x] Use asm-differ JSON output format (#130)

Things I can think of that would be nice:

• [ ] Click a jump to scroll to it
• [ ] Hover over a jump to highlight the target
• [x] Click* on a register to find all uses of it
• [x] Highlight the asm lines affected by the current line in the sourcecode editor
• [ ] Highlight the sourcecode line corresponding to the clicked asm line
• [x] Click a line number to jump to it in the source
• [ ] "Compress matching" option, like -U/-V in diff.py
• [ ] a mode where the source and diff scrolling is synced (eg. based on the line numbers currently displayed in the diff)
• [ ] "jump to first diff" button, or even forward/back buttons for cycling through diffs

@simonlindholm @zbanks @ethteck perhaps you have more ideas? edit the task list

[bates64]

#130 begins implementation of this :shipit: