Bug 139: portability fixes and documentation. Document the dynamic lookup module capability in spec.xfpt. Include a ChangeLog item. Avoid the GNU-specific "export" make(1) directive. Build the lookups Makefile using the existing framework. Build with BSD Make once more. The src/lookups/Makefile that is used at build time now has the dynamic content come from scripts/lookups-Makefile. Add CFLAGS_DYNAMIC support, which can be set in Local/Makefile. Provide defaults for Linux & FreeBSD. Ensure that build fails early if a dynamic module is requested but CFLAGS_DYNAMIC is not defined.