This is more correct: a pagelist is a linked list of nodes, not pages.
The nodes themselves contain pages but we were previously calling the
nodes "pages" which was confusing, especially as I plan some future
changes to the way pages are stored.
Fixes#1416
At a high level, the issue is that when mouse capture is enabled (i.e. in
neovim), "shift" escapes the capture. So "cmd+shift" is equal to "cmd"
which doesn't get sent to the TUI program and so on. For link
highlighting which now requires "cmd" (super) is held, we were sending
"cmd+shift" to the renderer so we weren't checking for links.
So the core of this commit is respecting this scenario and stripping the
shift modifier.
This commit also found that when the mouse wasn't over a link, we were
always checking and highlighting links on line one of the visible
screen. This bug is fixed and should also result in a very slight
performance improvement on rendering in all cases.
