IMPORT: slz: use inttypes.h instead of stdint.h

stdint.h is not as portable as inttypes.h. It doesn't exist at least
on AIX 5.1 and Solaris 7, while inttypes.h is present there and does
include stdint.h on platforms supporting it.

This is equivalent to libslz upstream commit e36710a ("slz: use
inttypes.h instead of stdint.h")
diff --git a/include/import/slz.h b/include/import/slz.h
index 0f284e3..d7d4863 100644
--- a/include/import/slz.h
+++ b/include/import/slz.h
@@ -25,7 +25,7 @@
 #ifndef _SLZ_H
 #define _SLZ_H
 
-#include <stdint.h>
+#include <inttypes.h>
 
 /* We have two macros UNALIGNED_LE_OK and UNALIGNED_FASTER. The latter indicates
  * that using unaligned data is faster than a simple shift. On x86 32-bit at