Add #include <new> to folly/Malloc.h.

Test Plan: folly tests

Reviewed By: philipp@fb.com, andrei.alexandrescu@fb.com

FB internal diff: D486884, D487376

folly/Malloc.h

@@ -32,6 +32,9 @@ namespace folly {
   using std::jemallocMinInPlaceExpandable;
   using std::usingJEMalloc;
   using std::smartRealloc;
+  using std::checkedMalloc;
+  using std::checkedCalloc;
+  using std::checkedRealloc;
 }
 
 #else // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
@@ -57,6 +60,8 @@ namespace folly {
 #include <cstdlib>
 #include <cstring>
 
+#include <new>
+
 /**
  * Declare rallocm() and malloc_usable_size() as weak symbols.  It
  * will be provided by jemalloc if we are using jemalloc, or it will