Build with newer Boost. From Fedora.

Index: gr-qtgui/lib/waterfall_sink_c_impl.cc
--- gr-qtgui/lib/waterfall_sink_c_impl.cc.orig
+++ gr-qtgui/lib/waterfall_sink_c_impl.cc
@@ -39,6 +39,8 @@
 namespace gr {
 namespace qtgui {
 
+using namespace boost::placeholders;
+
 waterfall_sink_c::sptr waterfall_sink_c::make(int fftsize,
                                               int wintype,
                                               double fc,
