OUStringBuffer to OUString and optimize related code
OUStringBuffer to OUString and optimize related code

Change-Id: I491fd1d1a8430457e681af2df723ef140cedc579

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