Strange Bro build problem with yacc/bison

I attempted to compile Bro 1.2 on a FreeBSD 6.1 box with yacc installed
and Bro complained of the following:

Yeah, we ran into this on a FreeBSD 6.1 machine too. It wasn't clear
at the time whether it was a general 6.1 problem or unique to our build;
I guess now we know :-).

I'm not sure what's the right autoconf goop to solve this - certainly
the current build failure isn't pretty.

    Vern

Such files should go into MOSTLYCLEANFILES. Try this:

Index: Makefile.am