Fix building on AIX 5.1

lib/legacy/zstd_v07.c

@@ -242,7 +242,11 @@ extern "C" {
 *  Basic Types
 *****************************************************************/
 #if  !defined (__VMS) && (defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
-# include <stdint.h>
+# if defined(_AIX)
+#  include <inttypes.h>
+# else
+#  include <stdint.h> /* intptr_t */
+# endif
   typedef  uint8_t BYTE;
   typedef uint16_t U16;
   typedef  int16_t S16;