const correct

Index: kernel/fhdl_stream.cc
--- kernel/fhdl_stream.cc.orig
+++ kernel/fhdl_stream.cc
@@ -4,6 +4,7 @@
 #endif
 #include <sstream>
 #include <assert.h>
+#include <string.h>
 #include <freehdl/kernel-error.hh>
 #include <freehdl/kernel-fhdl-stream.hh>
 
@@ -60,7 +61,7 @@ fhdl_ostream_t::bind_to_socket(int s) 
 }
 
 fhdl_ostream_t &
-fhdl_ostream_t::operator<<(char *p) 
+fhdl_ostream_t::operator<<(const char *p) 
 {
   if (!socket_connection)
     *str << p;