The long-term benefit will be support of C++11 char16_t string literals (for
cases of string literals with non-ASCII content) once we drop any compilers that
don't support those yet.  The short-term benefit is support for an improved
OUStringLiteral1 that accepts any sal_Unicode value, not just ASCII ones (see
next commit).

Change-Id: I3f8f6697d7eb62b5176b7e812b5a5113c53b83a4
Reviewed-on: https://gerrit.libreoffice.org/28445Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>