merging more memory fixes

libs/core/pxt.cpp

@@ -117,7 +117,6 @@ namespace pxt {
 
     void RefObject::destroy() {
       ((RefObjectMethod)getVTable()->methods[0])(this);
-      delete this;
     }
 
     void RefObject::print() {
@@ -245,6 +244,7 @@ namespace pxt {
           this->data[i] = 0;
         }
       this->data.resize(0);
+      delete this;
     }
 
     void RefCollection::print()
@@ -278,6 +278,7 @@ namespace pxt {
 
     void RefLocal::destroy()
     {
+      delete this;
     }
 
     PXT_VTABLE_CTOR(RefLocal) {
@@ -296,6 +297,7 @@ namespace pxt {
     void RefRefLocal::destroy()
     {
       decr(v);
+      delete this;
     }
 
     PXT_VTABLE_BEGIN(RefMap, 0, RefMapMarker)
@@ -310,6 +312,7 @@ namespace pxt {
         data[i].val = 0;
       }
       data.resize(0);
+      delete this;
     }
 
     int RefMap::findIdx(uint32_t key) {