Implement a new DEPENDS definition, which looks for an installed
package, building it if not present, and use it in preference to
LIB_DEPENDS. This should make the package collection more useful on
NetBSD ELF ports.
Generalise Local.config to use LOCALBASE and X11BASE definitions,
rather than using hard-coded paths.
Add PNG definitions to the *BSDArchitecture definitions in
Local.config
Correct LIB_DEPENDS lines for NetBSD.
Add CAT1 definition for preformatted manual page
Use sed to generalise LOCALBASE and X11BASE, rather than having
hard-coded paths.
