solarized: use VertSplit bg for inactive statusline

Adjust foreground color accordingly, also for non-active modified
filename (to stand out).
Merge branch 'solarized-inactive-like-vertsplit'
Revert changes to s:NM, add s:NMi for inactive windows
Revert changes to s:NM, add s:NMi for inactive windows
Merge branch 'solarized-inactive-like-vertsplit'