qmake messes up version header in Microsoft Visual Studio 2015 solution files

Problem: When generating Microsoft Visual Studio 2015 files for a qmake project with subdirs template the header of the generated .sln file is messed up because it both prints the header for version 2015 and 2013.

Steps to reproduce:
Generate a Microsoft Visual Studio 2015 project from the sample project in the attachment by issuing the following command:
qmake -r -tp vc -spec win32-msvc2015 project.pro