replace assert.h with cassert

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/net/AddressInfo.cxx

@@ -30,7 +30,7 @@
 #include "AddressInfo.hxx"
 #include "Features.hxx"
 
-#include <assert.h>
+#include <cassert>
 
 static constexpr int address_family_ranking[] = {
 #ifdef HAVE_UN

src/net/IPv4Address.cxx

@@ -29,7 +29,7 @@
 
 #include "IPv4Address.hxx"
 
-#include <assert.h>
+#include <cassert>
 
 static const struct sockaddr_in *
 CastToIPv4(const struct sockaddr *p) noexcept

src/net/IPv6Address.cxx

@@ -30,7 +30,8 @@
 #include "IPv6Address.hxx"
 #include "IPv4Address.hxx"
 
-#include <assert.h>
+#include <cassert>
+
 #include <string.h>
 
 static const struct sockaddr_in6 *

src/net/SocketAddress.cxx

@@ -32,7 +32,8 @@
 #include "IPv6Address.hxx"
 #include "util/StringView.hxx"
 
-#include <assert.h>
+#include <cassert>
+
 #include <string.h>
 
 #ifdef HAVE_UN

src/net/StaticSocketAddress.hxx

@@ -34,7 +34,7 @@
 #include "Features.hxx"
 #include "util/Compiler.h"
 
-#include <assert.h>
+#include <cassert>
 
 /**
  * An OO wrapper for struct sockaddr_storage.

src/net/ToString.cxx

@@ -34,6 +34,7 @@
 #include "IPv4Address.hxx"
 
 #include <algorithm>
+#include <cassert>
 
 #ifdef _WIN32
 #include <ws2tcpip.h>
@@ -48,7 +49,6 @@
 #include <sys/un.h>
 #endif
 
-#include <assert.h>
 #include <string.h>
 
 #ifdef HAVE_UN