silence boost Unknown compiler version message with VS2012
silence boost Unknown compiler version message with VS2012

Change-Id: I8f81cc7491da81c33bd27d084a8e7b19e5c637a7
Reviewed-on: https://gerrit.libreoffice.org/784
Reviewed-by: Norbert Thiebaud <4a068946920c47769d700757a47cfec2afcce997@gmail.com>
Tested-by: Norbert Thiebaud <4a068946920c47769d700757a47cfec2afcce997@gmail.com>

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core