Add vector utility functions

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Makefile

@@ -103,6 +103,7 @@ OBJECTS += ui-stats.o
 OBJECTS += ui-summary.o
 OBJECTS += ui-tag.o
 OBJECTS += ui-tree.o
+OBJECTS += vector.o
 
 ifdef NEEDS_LIBICONV
 	EXTLIBS += -liconv