Fix compiler errors.

On Mavericks with Apple's Clang 5.0 (3.3 based):
../3rdparty/javascriptcore/JavaScriptCore/runtime/Structure.h:320:117: error: non-const reference cannot bind to bit-field 'm_attributesInPrevious'
  ...add(StructureTransitionTableHash::Key(RefPtr<UString::Rep>(existingTransition->m_nameInPrevious.get()), existingTransition->m_attributesInPrevious), exi...
                                                                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

C++11 specific:
../3rdparty/javascriptcore/JavaScriptCore/bytecompiler/BytecodeGenerator.h:179:35: error: non-constant-expression cannot be narrowed from type 'size_t'
      (aka 'unsigned long') to 'uint32_t' (aka 'unsigned int') in initializer list [-Wc++11-narrowing]
                LineInfo info = { instructions().size(), n->lineNo() };
                                  ^~~~~~~~~~~~~~~~~~~~~

Both occur in multiple places.

Task-number: QTBUG-34842

Change-Id: I98a29b51718a6e0db8749ac1b495e071e9fe479d
Reviewed-by: Lars Knoll <lars.knoll@digia.com>