Build with newer Boost. From Fedora.

Index: gr-blocks/lib/repeat_impl.cc
--- gr-blocks/lib/repeat_impl.cc.orig
+++ gr-blocks/lib/repeat_impl.cc
@@ -30,6 +30,8 @@
 namespace gr {
 namespace blocks {
 
+using namespace boost::placeholders;
+
 repeat::sptr repeat::make(size_t itemsize, int interp)
 {
     return gnuradio::get_initial_sptr(new repeat_impl(itemsize, interp));
