added tests for dbi_driver_encoding_from_iana() and dbi_driver_encoding_to_iana()
added tests for dbi_driver_encoding_from_iana() and dbi_driver_encoding_to_iana()

cention-nazri/libdbi-drivers,cention-nazri/libdbi-drivers,cention-nazri/libdbi-drivers,cention-nazri/libdbi-drivers