Minor improvement suggestion for Terminal usage documentation

[Vilius Panevėžys]

After setting up a Debian 9 "stretch" system, which ships Xfce 4.12.3
and Terminal 0.8.3, I promptly noticed Shift+Up/Down no longer work for
line scrolling. I quickly came across the behaviour change note [1],
but it took me more time than necessary to understand what's been done
[2], why [3] and how to configure the old behaviour [4].

I think it would be useful to note the hidden option to restore the old
behaviour right where the behaviour change is mentioned. Please find
the diff for suggested change attached. I couldn't find the
documentation repo (www/docs.xfce.org seems out of date with what is
currently hosted on the domain), so I generated a unified diff against
the saved page source. It would be nice to add this before stretch is
released as that would hopefully save some time for thousands of
Terminal users in Debian.

By the way, in my opinion the new default line scrolling keyboard
shortcut is inconvenient - it's cumbersome to quickly use both page
scrolling and line scrolling (move a few screens back, then adjust by a
few lines) because of differing modifiers (Shift and Ctrl+Shift).
Another problem with using page and line scrolling shortcuts in quick
succession is that due to differing modifiers it's easy to mistake
Ctrl+Shift+PgUp/PgDown (move tab) for Shift+PgUp/PgDown (scroll page).
Using only the Shift modifier for both page and line scrolling does not
have these problems.


[1]
http://docs.xfce.org/apps/terminal/usage#to_work_with_the_contents_of_terminal_windows
[2]
https://git.xfce.org/apps/xfce4-terminal/commit/?id=4cf4d385b952e770d2e353941dc14934d9bb8d8c
[3] https://bugzilla.xfce.org/show_bug.cgi?id=12816
[4]
https://git.xfce.org/apps/xfce4-terminal/commit/?id=16c47b9eccb3095f893675ba84f6ceeed816252e
[5] http://docs.xfce.org/apps/terminal/advanced#hidden_options