Note: this maps to /Z7 apparently:
<DebugInformationFormat>OldStyle</DebugInformationFormat>

https://msdn.microsoft.com/en-us/library/bb629394.aspx
lists various options but passing /p:DebugSymbols=true /p:DebugType=full
/p:PdbFile=... to msbuild.exe by itself doesn't do anything while
patching the project file works.

Change-Id: I888b5f6af7be519e2d35b749873ae7d35bb0bf9d
Reviewed-on: https://gerrit.libreoffice.org/56605
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>