[coretext/uniscribe] Fix build

https://travis-ci.org/behdad/harfbuzz/jobs/295039536#L3468
https://ci.appveyor.com/project/behdad/harfbuzz/build/1.0.697/job/dr1ujlntxafeqbej#L142

src/hb-coretext.cc

@@ -351,7 +351,9 @@ struct active_feature_t {
   feature_record_t rec;
   unsigned int order;
 
-  static int cmp (const active_feature_t *a, const active_feature_t *b) {
+  static int cmp (const void *pa, const void *pb) {
+    const active_feature_t *a = (const active_feature_t *) pa;
+    const active_feature_t *b = (const active_feature_t *) pb;
     return a->rec.feature < b->rec.feature ? -1 : a->rec.feature > b->rec.feature ? 1 :
 	   a->order < b->order ? -1 : a->order > b->order ? 1 :
 	   a->rec.setting < b->rec.setting ? -1 : a->rec.setting > b->rec.setting ? 1 :
@@ -367,7 +369,9 @@ struct feature_event_t {
   bool start;
   active_feature_t feature;
 
-  static int cmp (const feature_event_t *a, const feature_event_t *b) {
+  static int cmp (const void *pa, const void *pb) {
+    const feature_event_t *a = (const feature_event_t *) pa;
+    const feature_event_t *b = (const feature_event_t *) pb;
     return a->index < b->index ? -1 : a->index > b->index ? 1 :
 	   a->start < b->start ? -1 : a->start > b->start ? 1 :
 	   active_feature_t::cmp (&a->feature, &b->feature);

src/hb-uniscribe.cc

@@ -264,7 +264,9 @@ struct active_feature_t {
   OPENTYPE_FEATURE_RECORD rec;
   unsigned int order;
 
-  static int cmp (const active_feature_t *a, const active_feature_t *b) {
+  static int cmp (const void *pa, const void *pb) {
+    const active_feature_t *a = (const active_feature_t *) pa;
+    const active_feature_t *b = (const active_feature_t *) pb;
     return a->rec.tagFeature < b->rec.tagFeature ? -1 : a->rec.tagFeature > b->rec.tagFeature ? 1 :
 	   a->order < b->order ? -1 : a->order > b->order ? 1 :
 	   a->rec.lParameter < b->rec.lParameter ? -1 : a->rec.lParameter > b->rec.lParameter ? 1 :
@@ -280,7 +282,9 @@ struct feature_event_t {
   bool start;
   active_feature_t feature;
 
-  static int cmp (const feature_event_t *a, const feature_event_t *b) {
+  static int cmp (const void *pa, const void *pb) {
+    const feature_event_t *a = (const feature_event_t *) pa;
+    const feature_event_t *b = (const feature_event_t *) pb;
     return a->index < b->index ? -1 : a->index > b->index ? 1 :
 	   a->start < b->start ? -1 : a->start > b->start ? 1 :
 	   active_feature_t::cmp (&a->feature, &b->feature);