MSVC makefiles generated by qmake fail to install PDB files

Makefiles generated by qmake for nmake on Windows build PDB files called "project.vc.pdb", but install targets try to install "project.pdb" and naturally fail.

Looking at the source code for qmake, this would seem be because, in msvc_nmake.cpp, NmakeMakefileGenerator::init() adds ".vc" to PDB file names, but NmakeMakefileGenerator::defaultInstall() does not.