Refactor and modernize namespace declarations

 * Completely remove inline namespace v2
 * Flatten some unnecessarily deep namespace nesting
 * Move DummyClientFace, Segmenter, SegmentFetcher to namespace ndn
 * Move all unit tests to namespace ndn::tests

Change-Id: I8bcfcf9fd669936a3277d2d5d505f765b4b05742
diff --git a/tests/benchmarks/encoding-bench.cpp b/tests/benchmarks/encoding-bench.cpp
index 1adb452..a3e0b5e 100644
--- a/tests/benchmarks/encoding-bench.cpp
+++ b/tests/benchmarks/encoding-bench.cpp
@@ -30,11 +30,7 @@
 
 #include <iostream>
 
-namespace ndn {
-namespace tlv {
-namespace tests {
-
-using namespace ndn::tests;
+namespace ndn::tests {
 
 template<size_t WIRE_SIZE>
 struct ReadVarNumberTest;
@@ -112,7 +108,7 @@
     uint64_t number = 0;
     for (int i = 0; i < N_ITERATIONS; ++i) {
       const uint8_t* begin2 = begin; // make a copy because readVarNumber increments the pointer
-      nOks += readVarNumber(begin2, end, number);
+      nOks += tlv::readVarNumber(begin2, end, number);
       nCorrects += number == Test::VALUE;
       // use the number and the return value, so compiler won't optimize out their computation
     }
@@ -124,6 +120,4 @@
             << " " << d << std::endl;
 }
 
-} // namespace tests
-} // namespace tlv
-} // namespace ndn
+} // namespace ndn::tests