There is no need to install avrdude.conf twice.  Remove the CONF_FILES_PERMS
entry, as the permissions are not exotic.
rectify sed pattern for guile version check in graphviz
GCC now wants zlib - and comes with an internal copy as an alternative to
using the system/Pkgsrc zlib.  At least on Ubuntu, the internal zlib fails to
get past configuration.

Use the standard Pkgsrc (or builtin) zlib instead.

Bump PKGREVISION to reflect the minor difference in build strategy.