vi: allow writing to another file if this one is readonly

Version 2. Same change but rebased after Ron's improvements. Fixes bug
where if you open a read only file, you can't save it as a different
filename.

function                                             old     new   delta
colon                                               3160    3162      +2

Signed-off-by: Alison Winters <alisonatwork@outlook.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed