If it exists, use /usr/ports/infrastructure/man/ by default for apropos(1);

we already used it by default for man(1) before.
While here, fix the order of Xenocara and ports.
ok millert@ sthen@

src/etc/man.conf

@@ -1,12 +1,13 @@
-#	$OpenBSD: man.conf,v 1.20 2014/02/24 20:11:53 espie Exp $
+#	$OpenBSD: man.conf,v 1.21 2014/12/09 05:55:42 schwarze Exp $
 
 # Sheer, raging paranoia...
 _version	BSD.2
 
 # The whatis/apropos database.
 _whatdb		/usr/share/man/whatis.db
-_whatdb		/usr/local/man/whatis.db
 _whatdb		/usr/X11R6/man/whatis.db
+_whatdb		/usr/ports/infrastructure/man/whatis.db
+_whatdb		/usr/local/man/whatis.db
 
 # Subdirectories for paths ending in '/', IN SEARCH ORDER.
 _subdir		{cat,man}1 {cat,man}8 {cat,man}6 {cat,man}2 {cat,man}3 {cat,man}5 {cat,man}7 {cat,man}4 {cat,man}9 {cat,man}3p {cat,man}3f {cat,man}n