This has the disadvantage that it makes comparisons involving fast
OUString concatenation via operator+ ambiguous, as can be seen in
scriptdlg.cxx, but it allows comparing String and OUString wihout
explicit conversion, which is nice for incrementally converting code.

Change-Id: Ibfc728bdb161a01e0f8311915c97bcbba8b58c0b
Reviewed-on: https://gerrit.libreoffice.org/1803Reviewed-by: Luboš Luňák <l.lunak@suse.cz>
Tested-by: Luboš Luňák <l.lunak@suse.cz>