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/lib/xiph/OggPage.hxx

@@ -23,9 +23,9 @@
 #include <ogg/ogg.h>
 
 #include <cassert>
+#include <cstdint>
 
 #include <string.h>
-#include <stdint.h>
 
 static size_t
 ReadPage(const ogg_page &page, void *_buffer, size_t size) noexcept

src/lib/xiph/OggStreamState.hxx

@@ -23,9 +23,9 @@
 #include <ogg/ogg.h>
 
 #include <cassert>
+#include <cstdint>
 
 #include <string.h>
-#include <stdint.h>
 
 class OggStreamState {
 	ogg_stream_state state;

src/lib/xiph/OggSyncState.hxx

@@ -23,8 +23,7 @@
 #include <ogg/ogg.h>
 
 #include <cstddef>
-
-#include <stdint.h>
+#include <cstdint>
 
 class Reader;