bug#24347: Bug when grepping a text file with some arbitrary binary data

[Paul Eggert]

>> The latter has been longstanding behavior for quite some time.
> I surmise it has not hit many distros yet.

The behavior with NULs was introduced in grep 2.3 (1999) so I think it has hit 
most distros by now....

Before 1999, grep was pickier about binary files than it is now; for example, 
ESC ('\033') was considered binary. No matter what heuristic we use for 
detecting binary files, the heuristic will break for some people and they will 
file bug reports. We have to use our best judgment, is all. In practice for 
today's files, NUL bytes are a pretty good sign that a file is binary.