mouse cannot be used in *grep* buffer if font-lock is turned off

[Drew Adams]

In Emacs 20, the mouse-face text property remains on entries in the *grep*
buffer, regardless of whether or not font-lock-mode is on.

In Emacs 21, if I turn off font-lock-mode, the mouse-face property also
disappears, and I cannot use mouse-2 to choose an entry.

In GNU Emacs 21.3.50.1 (i386-mingw-nt5.1.2600)
 of 2004-07-26 on BERATUNG4
configured using `configure --with-gcc
(3.3) --cflags -I../../jpeg-6b-1/include -I../../libpng-1.2.4-1/include -I..
/../tiff-3.5.7/include -I../../xpm-nox-4.2.0/include -I../../zlib-1.1.4-1/in
clude'