perf strlist: Make dupstr be the default and part of an extensible config parm

So that we can pass more info to strlist__new() without having to change
its function signature, just adding entries to the strlist_config struct
with sensible defaults for when those fields are not specified.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-5uaaler4931i0s9sedxjquhq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-finder.c

@@ -1355,7 +1355,7 @@ static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
 		 vl->point.offset);
 
 	/* Find local variables */
-	vl->vars = strlist__new(true, NULL);
+	vl->vars = strlist__new(NULL, NULL);
 	if (vl->vars == NULL)
 		return -ENOMEM;
 	af->child = true;