UIDNA_CHECK_CONTEXTO is only available in ICU >= 49

...unlike the rest of the createUTS46Instance stuff, which is available in 4.6.
While it is desirable to have that check here, it probably doesn't make much of
a difference in practice, and Rico Tzschichholz would like to have this working
on Ubuntu 12.04, where only ICU 4.8.1 is available.

Change-Id: I5bbd2ed296c6e068e175e7f8353cea37ed4d9e44

svl/source/misc/urihelper.cxx

@@ -763,7 +763,10 @@ OUString URIHelper::resolveIdnaHost(OUString const & url) {
     std::unique_ptr<icu::IDNA> idna(
         icu::IDNA::createUTS46Instance(
             (UIDNA_USE_STD3_RULES | UIDNA_CHECK_BIDI | UIDNA_CHECK_CONTEXTJ
-             | UIDNA_CHECK_CONTEXTO),
+#if U_ICU_VERSION_MAJOR_NUM >= 49
+             | UIDNA_CHECK_CONTEXTO
+#endif
+             ),
             e));
     if (U_FAILURE(e)) {
         SAL_WARN("vcl.gdi", "icu::IDNA::createUTS46Instance " << e);