extensions: Use appropriate OUString functions on string constants
extensions: Use appropriate OUString functions on string constants

Change-Id: Ief21a59fc58cdd6fb3398bbe5080ed5a53cb374e

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