String to OUString applied in dbaccess/source/ext/macromigration module.
Also, RTL_CONSTASCII_USTRINGPARAM is removed from files, plus
::rtl::OUString replaced by OUString.

Change-Id: I31673c7d812992dbac675a5d7da5bf379c402a9c
Reviewed-on: https://gerrit.libreoffice.org/2379Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>