Replace a couple of malloc()s with calloc()

src/hb-face.cc

diff --git a/src/hb-face.cc b/src/hb-face.cc
index 7aa89fc..9effc41 100644
--- a/src/hb-face.cc
+++ b/src/hb-face.cc
@@ -113,7 +113,7 @@
 {
   hb_face_for_data_closure_t *closure;
 
-  closure = (hb_face_for_data_closure_t *) malloc (sizeof (hb_face_for_data_closure_t));
+  closure = (hb_face_for_data_closure_t *) calloc (1, sizeof (hb_face_for_data_closure_t));
   if (unlikely (!closure))
     return NULL;