convert vcl/inc/fontsubset.hxx from String to OUString
convert vcl/inc/fontsubset.hxx from String to OUString

Change-Id: I0b57858a4a63a6e53883f053c6a3a8a494a422dc

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