Fix horizontal offset when enabling word-wrap

[Yukigaru]

When a view is scrolled horizontally (left > 0) with word-wrap disabled, enabling word-wrap doesn't reset horizontal offset and keep user stuck in that shifted view.

Reproduction steps:

• open a file with lines longer than your view
• disable wrap
• scroll right
• enable wrap
• now you don't see line beginnings and you're stuck in that horizontal offset until you disable wrap again.

Fix: reset that offset when word-wrap is enabled.

[tstack]

Thanks! I think I messed this up when I changed the handling of CTRL-W from being hardcoded to doing an UPDATE on the lnav_views table.