Replace ARDUINOJSON_NAMESPACE with an inline namespace (#1820)

extras/tests/JsonDocument/BasicJsonDocument.cpp

@@ -8,8 +8,6 @@
 #include <sstream>
 #include <utility>
 
-using ARDUINOJSON_NAMESPACE::addPadding;
-
 class SpyingAllocator {
  public:
   SpyingAllocator(const SpyingAllocator& src) : _log(src._log) {}

extras/tests/JsonDocument/DynamicJsonDocument.cpp

@@ -5,7 +5,7 @@
 #include <ArduinoJson.h>
 #include <catch.hpp>
 
-using ARDUINOJSON_NAMESPACE::addPadding;
+using ArduinoJson::detail::addPadding;
 
 static void REQUIRE_JSON(JsonDocument& doc, const std::string& expected) {
   std::string json;

extras/tests/JsonDocument/ElementProxy.cpp

@@ -5,7 +5,7 @@
 #include <ArduinoJson.h>
 #include <catch.hpp>
 
-typedef ARDUINOJSON_NAMESPACE::ElementProxy<JsonDocument&> ElementProxy;
+typedef ArduinoJson::detail::ElementProxy<JsonDocument&> ElementProxy;
 
 TEST_CASE("ElementProxy::add()") {
   DynamicJsonDocument doc(4096);

extras/tests/JsonDocument/MemberProxy.cpp

@@ -5,7 +5,7 @@
 #include <ArduinoJson.h>
 #include <catch.hpp>
 
-typedef ARDUINOJSON_NAMESPACE::MemberProxy<JsonDocument&, const char*>
+typedef ArduinoJson::detail::MemberProxy<JsonDocument&, const char*>
     MemberProxy;
 
 TEST_CASE("MemberProxy::add()") {

extras/tests/JsonDocument/shrinkToFit.cpp

@@ -8,8 +8,6 @@
 #include <stdlib.h>  // malloc, free
 #include <string>
 
-using ARDUINOJSON_NAMESPACE::addPadding;
-
 class ArmoredAllocator {
  public:
   ArmoredAllocator() : _ptr(0), _size(0) {}