clang-tidy: use C++ headers

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

src/convert.cpp

@@ -26,8 +26,8 @@
 #endif
 
 #ifdef EXV_HAVE_ICONV
-#include <errno.h>
 #include <iconv.h>
+#include <cerrno>
 #endif
 
 // Adobe XMP Toolkit

src/http.cpp

@@ -23,12 +23,12 @@
 #define closesocket close
 
 #include <arpa/inet.h>
-#include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <unistd.h>
+#include <cerrno>
 
 #define fopen_S(f, n, o) f = fopen(n, o)
 #define WINAPI

unitTests/test_slice.cpp

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <gtest/gtest.h>
-#include <stdint.h>
+#include <cstdint>
 #include <exiv2/exiv2.hpp>
 #include "slice.hpp"
 #include "types.hpp"