fix include for AIX

apparently, AIX does not support <stdint.h>
even though it advertises being C99 compliant.

xxhash.h

@@ -589,7 +589,11 @@ typedef uint32_t XXH32_hash_t;
 #elif !defined (__VMS) \
   && (defined (__cplusplus) \
   || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
-#   include <stdint.h>
+#   ifdef _AIX
+#     include <inttypes.h>
+#   else
+#     include <stdint.h>
+#   endif
     typedef uint32_t XXH32_hash_t;
 
 #else
@@ -863,7 +867,11 @@ typedef uint64_t XXH64_hash_t;
 #elif !defined (__VMS) \
   && (defined (__cplusplus) \
   || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
-#  include <stdint.h>
+#   ifdef _AIX
+#     include <inttypes.h>
+#   else
+#     include <stdint.h>
+#   endif
    typedef uint64_t XXH64_hash_t;
 #else
 #  include <limits.h>
@@ -2479,10 +2487,14 @@ static void* XXH_memcpy(void* dest, const void* src, size_t size)
 #if !defined (__VMS) \
  && (defined (__cplusplus) \
  || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
-# include <stdint.h>
-  typedef uint8_t xxh_u8;
+#   ifdef _AIX
+#     include <inttypes.h>
+#   else
+#     include <stdint.h>
+#   endif
+    typedef uint8_t xxh_u8;
 #else
-  typedef unsigned char xxh_u8;
+    typedef unsigned char xxh_u8;
 #endif
 typedef XXH32_hash_t xxh_u32;