Supporting Visual Studio 2013

Project files (.sln and .csproj) created for building VS2013 versions.
Precompiler define VS2013 added where needed.

Change-Id: I110d08cd8ba91c04b07eb56f837a181a1246f11a
Reviewed-by: Torben Dannhauer <torben@dannhauer.info>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>