utils: Include stdint.h

Recent releases of glibc don't include the full stdint.h header in some
network headers included by utils.h.  So uintptr_t might not be defined.
Since we use fixed width integers, including the latter, all over the place
we make sure the complete file is included.

Fixes #2425.

src/libstrongswan/utils/utils.h

@@ -25,6 +25,7 @@
 #define _GNU_SOURCE
 #include <sys/types.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <stddef.h>
 #include <sys/time.h>
 #include <string.h>