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;
 

src/hb-shape-plan.cc

diff --git a/src/hb-shape-plan.cc b/src/hb-shape-plan.cc
index 1d94c52..56e2ea5 100644
--- a/src/hb-shape-plan.cc
+++ b/src/hb-shape-plan.cc
@@ -128,7 +128,7 @@
     face = hb_face_get_empty ();
   if (unlikely (!props))
     return hb_shape_plan_get_empty ();
-  if (num_user_features && !(features = (hb_feature_t *) malloc (num_user_features * sizeof (hb_feature_t))))
+  if (num_user_features && !(features = (hb_feature_t *) calloc (num_user_features, sizeof (hb_feature_t))))
     return hb_shape_plan_get_empty ();
   if (!(shape_plan = hb_object_create<hb_shape_plan_t> ())) {
     free (features);

src/hb-shaper.cc

diff --git a/src/hb-shaper.cc b/src/hb-shaper.cc
index 580b95c..b25566d 100644
--- a/src/hb-shaper.cc
+++ b/src/hb-shaper.cc
@@ -64,7 +64,7 @@
     }
 
     /* Not found; allocate one. */
-    shapers = (hb_shaper_pair_t *) malloc (sizeof (all_shapers));
+    shapers = (hb_shaper_pair_t *) calloc (1, sizeof (all_shapers));
     if (unlikely (!shapers)) {
       (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, &all_shapers[0]);
       return (const hb_shaper_pair_t *) all_shapers;