bug#9990: valgrind warning in add_row_entry

[Eli Zaretskii]

> From: Dan Nicolaescu <dann@gnu.org>
> Cc: 9990@debbugs.gnu.org
> Date: Tue, 15 Nov 2011 12:21:56 -0500
> 
> BTW, why is the hash only using 28 bits instead of the full 32?  Won't
> it get a bit more precision if using 32?

I don't know.  I suspect this is simply history inherited from a
similar (but not identical -- why?) code in line_hash_code, which also
uses 28 bits.

Richard, do you remember by chance why only 28 bits are used?