replace stdint.h with cstdint

The former is deprecated by C++14. The standard says they are the same:

The header defines all types and macros the same as the C standard library
header<stdint.h>.

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

src/tag/Aiff.cxx

@@ -21,10 +21,10 @@
 #include "input/InputStream.hxx"
 #include "util/ByteOrder.hxx"
 
+#include <cstdint>
 #include <limits>
 #include <stdexcept>
 
-#include <stdint.h>
 #include <string.h>
 
 struct aiff_header {

src/tag/ApeLoader.cxx

@@ -23,9 +23,9 @@
 #include "util/StringView.hxx"
 
 #include <cassert>
+#include <cstdint>
 #include <memory>
 
-#include <stdint.h>
 #include <string.h>
 
 struct ApeFooter {

src/tag/Id3Picture.cxx

@@ -23,10 +23,9 @@
 #include "util/ConstBuffer.hxx"
 #include "util/StringView.hxx"
 
+#include <cstdint>
 #include <string>
 
-#include <stdint.h>
-
 static StringView
 ReadString(ConstBuffer<uint8_t> &src) noexcept
 {

src/tag/Mask.hxx

@@ -22,7 +22,7 @@
 
 #include "Type.h"
 
-#include <stdint.h>
+#include <cstdint>
 
 class TagMask {
 	typedef uint_least32_t mask_t;

src/tag/Pool.cxx

@@ -24,11 +24,11 @@
 #include "util/StringView.hxx"
 
 #include <cassert>
+#include <cstdint>
 #include <limits>
 
 #include <string.h>
 #include <stdlib.h>
-#include <stdint.h>
 
 Mutex tag_pool_lock;
 

src/tag/Riff.cxx

@@ -21,10 +21,10 @@
 #include "input/InputStream.hxx"
 #include "util/ByteOrder.hxx"
 
+#include <cstdint>
 #include <limits>
 #include <stdexcept>
 
-#include <stdint.h>
 #include <string.h>
 
 struct riff_header {

src/tag/Rva2.cxx

@@ -22,7 +22,8 @@
 
 #include <id3tag.h>
 
-#include <stdint.h>
+#include <cstdint>
+
 #include <string.h>
 
 enum class Rva2Channel : uint8_t {

src/tag/Type.h

@@ -21,7 +21,7 @@
 #define MPD_TAG_TYPE_H
 
 #ifdef __cplusplus
-#include <stdint.h>
+#include <cstdint>
 #endif
 
 /**