Fix Clang 3.9 compilation (#138)

tests/modcc/test_kinetic_rewriter.cpp

@@ -9,6 +9,7 @@
 #include "expr_expand.hpp"
 #include "test.hpp"
 
+using namespace nest::mc;
 
 stmt_list_type& proc_statements(Expression *e) {
     if (!e || !e->is_symbol() || ! e->is_symbol()->is_procedure()) {
@@ -95,4 +96,3 @@ TEST(KineticRewriter, equiv) {
     EXPECT_EQ(deriv_map["b'"], kin_map["b'"]);
     EXPECT_EQ(deriv_map["c'"], kin_map["c'"]);
 }
-

tests/modcc/test_optimization.cpp

@@ -5,6 +5,8 @@
 #include "constantfolder.hpp"
 #include "modccutil.hpp"
 
+using namespace nest::mc;
+
 TEST(Optimizer, constant_folding) {
     auto v = util::make_unique<ConstantFolderVisitor>();
     {

tests/modcc/test_visitors.cpp

@@ -10,6 +10,8 @@
  * visitors
  **************************************************************/
 
+using namespace nest::mc;
+
 TEST(FlopVisitor, basic) {
     {
     auto visitor = util::make_unique<FlopVisitor>();