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

3rdparty/libpng.vcxproj

@@ -28,6 +28,9 @@
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <PropertyGroup>
+    <PreferredToolArchitecture>x64</PreferredToolArchitecture>
+  </PropertyGroup>
   <ImportGroup Label="ExtensionSettings">
   </ImportGroup>
   <ImportGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|x64'" Label="PropertySheets">
@@ -97,7 +100,7 @@
       <DisableSpecificWarnings>$(DisableSpecificWarnings)</DisableSpecificWarnings>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <TreatWarningAsError>$(TreatWarningAsError)</TreatWarningAsError>
-      <Optimization>Full</Optimization>
+      <Optimization>MaxSpeed</Optimization>
       <WholeProgramOptimization>true</WholeProgramOptimization>
     </ClCompile>
     <Link>