sal logging: Flush after having written the output.

Makes it possible to see the messages immediately on Windows; otherwise the
SAL_DEBUG() etc. is useless as it shows on screen too late.

Change-Id: I701922aa4fcacf66d6b044e0badca7ef1f9cac94

sal/osl/all/log.cxx

@@ -240,6 +240,7 @@ void log(
 #endif
     } else {
         std::fputs(s.str().c_str(), stderr);
+        std::fflush(stderr);
     }
 #endif
 }