Add CLR 4.0 version string.

Author: jfreilly

src/AssemblyInfo.cs

@@ -49,6 +49,8 @@
 [assembly: AssemblyTitle("SharpZipLib for .NET Framework 3.0")]
 #elif (NET_3_5)
 [assembly: AssemblyTitle("SharpZipLib for .NET Framework 3.5")]
+#elif (NET_4_0)
+[assembly: AssemblyTitle("SharpZipLib for .NET Framework 4.0")]
 #elif (NETCF_1_0)
 [assembly: AssemblyTitle("SharpZipLib for .NET Compact Framework 1.0")]
 #elif (NETCF_2_0)