O[U]String overloads that return view for rest parameter

Add new overloads to OUString methods that have a
"OUString* rest" style parameter.

Instead return a view, which does not require allocation.

To avoid overload ambiguity, split the methods into
different variants that do not use default parameters.

Change-Id: I1aa366115750f1f7ea4fe665804195f59f7c4b69
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167632
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins

xmlhelp/source/cxxhelp/provider/databases.cxx

@@ -289,7 +289,7 @@ const std::vector< OUString >& Databases::getModuleList( const OUString& Languag
             fileName = aStatus.getFileName();
 
             // Check, whether fileName is of the form *.cfg
-            if (!fileName.endsWithIgnoreAsciiCase(".cfg", &fileName)) {
+            if (!fileName.endsWithIgnoreAsciiCase(u".cfg", &fileName)) {
                 continue;
             }
             fileName = fileName.toAsciiLowerCase();