Allocate HphpArrays in a flat mode instead of using m_inline_data

Gets HphpArrays into a flat mode using MM().objMalloc()
instead of SmartAllocator.  Various optimizations were needed to the
Make functions to get this to work out ok.  Growth still creates a
non-flat HphpArray (leaving a PromotedPayload behind so we know how
big the original allocation was).

Reviewed By: @edwinsmith

Differential Revision: D969431

hphp/runtime/base/array-init.cpp

@@ -30,13 +30,15 @@ ArrayInit::ArrayInit(ssize_t n) {
     // Force compilation of PolicyArray
     m_data = NEW(PolicyArray)(n);
   } else {
-    m_data = ArrayData::Make(n);
+    m_data = HphpArray::MakeReserve(n);
+    m_data->setRefCount(0);
   }
 }
 
 HOT_FUNC
 ArrayInit::ArrayInit(ssize_t n, MapInit)
-  : m_data(ArrayData::Make(n)) {
+  : m_data(HphpArray::MakeReserve(n)) {
+  m_data->setRefCount(0);
 }
 
 ///////////////////////////////////////////////////////////////////////////////