build: switch to C++17

Change-Id: Ia147b22fbdee68d87f0289851683ffbbb4466caa
diff --git a/src/clients/response.cpp b/src/clients/response.cpp
index 48b8a7d..4aedf73 100644
--- a/src/clients/response.cpp
+++ b/src/clients/response.cpp
@@ -163,14 +163,14 @@
 Response&
 Response::addRr(const Block& rr)
 {
-  this->m_rrs.push_back(rr);
+  m_rrs.push_back(rr);
   return *this;
 }
 
 Response&
 Response::addRr(const std::string& rr)
 {
-  return this->addRr(makeBinaryBlock(ndns::tlv::RrData, rr.c_str(), rr.size()));
+  return addRr(makeStringBlock(ndns::tlv::RrData, rr));
 }
 
 bool
diff --git a/src/clients/response.hpp b/src/clients/response.hpp
index 4e8f335..5417c8c 100644
--- a/src/clients/response.hpp
+++ b/src/clients/response.hpp
@@ -33,8 +33,7 @@
 /**
  * @brief Default life time of resource record
  */
-const time::seconds DEFAULT_RR_FRESHNESS_PERIOD = 3600_s;
-
+inline constexpr time::seconds DEFAULT_RR_FRESHNESS_PERIOD = 3600_s;
 
 /**
  * @brief NDNS Response abstraction. Response is used on client side,