Add a missing #include.

This causes compiler errors in some setups otherwise, e.g.:

  CC       libsigrokdecode_la-session.lo
session.c: In function 'srd_session_metadata_set':
session.c:195:46: error: expected ')' before 'PRIu64'
  srd_dbg("Setting session %d samplerate to %"PRIu64".",
                                              ^
session.c: In function 'srd_session_send':
session.c:242:15: error: expected ')' before 'PRIu64'
    "number %" PRIu64 ", %" PRIu64 " bytes at 0x%p",
               ^

1 files changed, 1 insertions, 0 deletions

diff --git a/session.c b/session.c
index 7eeab16..84c38a6 100644
--- a/session.c
+++ b/session.c
@@ -21,6 +21,7 @@
 #include "libsigrokdecode.h" /* First, so we avoid a _POSIX_C_SOURCE warning. */
 #include "libsigrokdecode-internal.h"
 #include "config.h"
+#include <inttypes.h>
 #include <glib.h>
 
 /**