Use OUStringBuffers for performance reasons.
Use OUStringBuffers for performance reasons.

Saves 120m pcycles in just 250k calls to ScAddress::Format.

Change-Id: Ibf20cf0843a47cf0fa37a38c4fecf1ae1560412c

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