Avoid a compile error which arises from a redefinition of "inline":

If it has been defined (by "configure", in "include/my_config.h"),
then an "#undef" is needed to avoid a redefinition.

This is needed to prevent a compile error of the debug server on AIX.

mysys/mf_keycache.c

@@ -325,6 +325,9 @@ static int keycache_pthread_cond_signal(pthread_cond_t *cond);
 #endif /* defined(KEYCACHE_DEBUG) */
 
 #if !defined(DBUG_OFF)
+#if defined(inline)
+#undef inline
+#endif
 #define inline  /* disabled inline for easier debugging */
 static int fail_block(BLOCK_LINK *block);
 static int fail_hlink(HASH_LINK *hlink);