each file independently from other files. The new semantics are
desired in the most of practical cases, e.g.: delete lines 5-9
from each file.
Keep the previous semantics of -i under a new option, -I, which
uses a single continuous address space covering all files to edit
in-place -- they are too cool to just drop them.
Add regression tests for -i and -I.
Approved by: dds
Compared with: GNU sed
Discussed on: -hackers
MFC after: 2 weeks
f6703c9c0a