Fix typo

examples/demangled_names.cpp

@@ -14,7 +14,7 @@
 
 #include <boost/type_index.hpp>
 #include <iostream>
-using bti = boost::typeind;
+namespace bti = boost::typeind;
 
 template <class T>
 void foo(T) {

examples/exact_types_match.cpp

@@ -18,7 +18,7 @@
 #include <iostream>
 #include <stdexcept>
 #include <cassert>
-using bti = boost::typeind;
+namespace bti = boost::typeind;
 
 class type_erased_unary_function {
     void*               function_ptr_;

examples/inheritance.cpp

@@ -14,7 +14,7 @@
 
 #include <boost/type_index.hpp>
 #include <iostream>
-using bti = boost::typeind;
+namespace bti = boost::typeind;
 
 struct A {
     BOOST_TYPE_INDEX_REGISTER_CLASS

examples/registry.cpp

@@ -14,7 +14,7 @@
 #include <boost/unordered_set.hpp>
 #include <boost/functional/hash.hpp>
 #include <cassert>
-using bti = boost::typeind;
+namespace bti = boost::typeind;
 
 int main() {
     boost::unordered_set<bti::type_index> types;