tidy: add readability-redundant-declaration

src/.clang-tidy

@@ -1,2 +1,11 @@
-Checks:          '-*,bugprone-argument-comment,modernize-use-nullptr'
-WarningsAsErrors: 'bugprone-argument-comment,modernize-use-nullptr'
+Checks: '
+-*,
+bugprone-argument-comment,
+modernize-use-nullptr,
+readability-redundant-declaration,
+'
+WarningsAsErrors: '
+bugprone-argument-comment,
+modernize-use-nullptr,
+readability-redundant-declaration,
+'

src/netaddress.cpp

@@ -20,9 +20,6 @@
 #include <iterator>
 #include <tuple>
 
-constexpr size_t CNetAddr::V1_SERIALIZATION_SIZE;
-constexpr size_t CNetAddr::MAX_ADDRV2_SIZE;
-
 CNetAddr::BIP155Network CNetAddr::GetBIP155Network() const
 {
     switch (m_net) {

src/randomenv.cpp

@@ -57,8 +57,7 @@
 #include <sys/auxv.h>
 #endif
 
-//! Necessary on some platforms
-extern char** environ;
+extern char** environ; // NOLINT(readability-redundant-declaration): Necessary on some platforms
 
 namespace {