pfunct: Use zalloc() to make the code more robust

Recently we had a problem where it was assumed that a field was
initialized to zeros but the constructor was using malloc(), check all
use and switch the ones allocating structs to zalloc() to prevent such
problems if we add extra fields to those structs.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/pfunct.c b/pfunct.c
index f42bdd1..5d34bc5 100644
--- a/pfunct.c
+++ b/pfunct.c
@@ -53,7 +53,7 @@
 
 static struct fn_stats *fn_stats__new(struct tag *tag, const struct cu *cu)
 {
-	struct fn_stats *stats = malloc(sizeof(*stats));
+	struct fn_stats *stats = zalloc(sizeof(*stats));
 
 	if (stats != NULL) {
 		const struct function *fn = tag__function(tag);