MSVC changes

Add support for compilation on x64 toolchain (x86 cl.exe was running out of heap space in vm.cpp)

Also took the opportunity to change compile optimisation from /Ox to /O2, as /O2 provides better optimisation than does /Ox

Also, we shouldn't be explicitely setting compiler tool defines (__cpp_lib_bitops), so remove that from types.h

llvm_build/llvm_build.vcxproj

@@ -26,6 +26,9 @@
     <UseDebugLibraries>false</UseDebugLibraries>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <PropertyGroup>
+    <PreferredToolArchitecture>x64</PreferredToolArchitecture>
+  </PropertyGroup>
   <ImportGroup Label="ExtensionSettings">
   </ImportGroup>
   <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="PropertySheets">