fix vs2013 build, constexpr require VC++ November 2013 CTP update

Visual C++ Compiler November 2013 CTP
http://www.microsoft.com/en-us/download/details.aspx?id=41151

README.md

@@ -7,7 +7,7 @@ Requires gcc 4.6 and higher, boost 1.46 and higher, crypto++
 
 on Windows
 
-Requires msvs2013, boost 1.46 and higher, crypto++
+Requires msvs2013 (require Visual C++ Compiler November 2013 CTP update), boost 1.46 and higher, crypto++
 
 Build Statuses
 ---------------

Win32/i2pd.vcxproj

@@ -92,7 +92,7 @@
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>true</UseDebugLibraries>
-    <PlatformToolset>v120</PlatformToolset>
+    <PlatformToolset>CTP_Nov2013</PlatformToolset>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
@@ -158,4 +158,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>