Patch from Colin Watson intended to give a clean Unix compile with GCC 4.

Patch from Colin Watson intended to give a clean Unix compile with GCC 4.
(Since we choose to compile with -Werror, this is particularly important.)

I haven't yet checked that the resulting source actually compiles cleanly with
GCC 4, hence not marking `gcc4-warnings' as fixed just yet.

[originally from svn r7041]