grep -r: add default "."

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I often forget the "." at the end of my 'grep -r'.
GNU grep automatically adds it, i.e.:

# grep -r foo
#

is the same as

# grep -r foo .
#

The grep we have in NetBSD recognizes that something is wrong, but is
not that helpful:

# grep -r foo
grep: warning: recursive search of stdin
(stops here, waiting for input)

I'd like the change the behaviour to match what GNU grep does.
Comments?
 Thomas