sdbus++: generate signal broadcast bindings

Change-Id: If1b04fedc95614c95a23768f95801e2bb9b4c0e9
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/tools/templates/interface.mako.server.hpp b/tools/templates/interface.mako.server.hpp
index 1d23646..73aff6b 100644
--- a/tools/templates/interface.mako.server.hpp
+++ b/tools/templates/interface.mako.server.hpp
@@ -43,6 +43,10 @@
 ${ m.cpp_prototype(loader, interface=interface, ptype='header') }
     % endfor
 
+    % for s in interface.signals:
+${ s.cpp_prototype(loader, interface=interface, ptype='header') }
+    % endfor
+
     private:
     % for m in interface.methods:
 ${ m.cpp_prototype(loader, interface=interface, ptype='callback-header') }