Use static_cast<> for NULL (clang 3.7)

The following errors come up when compiling v8
 with clang 3.7 on FreeBSD/amd64:

src/runtime/runtime-i18n.cc:629:37: error: reinterpret_cast from
'nullptr_t' to 'v8::internal::Smi *' is not allowed
  local_object->SetInternalField(1, reinterpret_cast<Smi*>(NULL));
                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

test/cctest/test-heap.cc:131:20: error: reinterpret_cast from
      'nullptr_t' to 'v8::internal::Object *' is not allowed
  Handle<Object> n(reinterpret_cast<Object*>(NULL), isolate);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test/cctest/test-heap.cc:1989:18: error: reinterpret_cast from
      'nullptr_t' to 'Address' (aka 'unsigned char *') is not
      allowed
  Address base = reinterpret_cast<Address>(NULL);
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+add myself to the AUTHORS file.

BUG=

Review URL: https://codereview.chromium.org/1277353002

Cr-Commit-Position: refs/heads/master@{#30103}

AUTHORS

@@ -69,6 +69,7 @@ Kang-Hao (Kenny) Lu <[email protected]>
 Luis Reis <[email protected]>
 Luke Zarko <[email protected]>
 Maciej Małecki <[email protected]>
+Marcin Cieślak <[email protected]>
 Mathias Bynens <[email protected]>
 Matt Hanselman <[email protected]>
 Matthew Sporleder <[email protected]>

src/runtime/runtime-i18n.cc

@@ -626,7 +626,7 @@ RUNTIME_FUNCTION(Runtime_CreateBreakIterator) {
 
   local_object->SetInternalField(0, reinterpret_cast<Smi*>(break_iterator));
   // Make sure that the pointer to adopted text is NULL.
-  local_object->SetInternalField(1, reinterpret_cast<Smi*>(NULL));
+  local_object->SetInternalField(1, static_cast<Smi*>(nullptr));
 
   Factory* factory = isolate->factory();
   Handle<String> key = factory->NewStringFromStaticChars("breakIterator");

test/cctest/test-heap.cc

@@ -127,7 +127,7 @@ TEST(HandleNull) {
   Isolate* isolate = CcTest::i_isolate();
   HandleScope outer_scope(isolate);
   LocalContext context;
-  Handle<Object> n(reinterpret_cast<Object*>(NULL), isolate);
+  Handle<Object> n(static_cast<Object*>(nullptr), isolate);
   CHECK(!n.is_null());
 }
 
@@ -1855,7 +1855,7 @@ TEST(TestAlignmentCalculations) {
       Heap::GetMaximumFillToAlign(kSimd128Unaligned);
   CHECK_EQ(maximum_simd128_misalignment, max_simd128_unaligned_fill);
 
-  Address base = reinterpret_cast<Address>(NULL);
+  Address base = static_cast<Address>(NULL);
   int fill = 0;
 
   // Word alignment never requires fill.