Use the LZ4 algorithm to compress metadata when the corresponding feature is enabled

*** 21,30 ****
--- 21,31 ----
  
  /*
   * Copyright (c) 2013 by Delphix. All rights reserved.
   * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
   * Copyright (c) 2013, Joyent, Inc. All rights reserved.
+  * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
   */
  
  #ifdef _KERNEL
  #include <sys/systm.h>
  #else
*** 167,177 ****
              B_FALSE, NULL);
  
          zfeature_register(SPA_FEATURE_LZ4_COMPRESS,
              "org.illumos:lz4_compress", "lz4_compress",
              "LZ4 compression algorithm support.", B_FALSE, B_FALSE,
!             B_FALSE, NULL);
  
          zfeature_register(SPA_FEATURE_MULTI_VDEV_CRASH_DUMP,
              "com.joyent:multi_vdev_crash_dump", "multi_vdev_crash_dump",
              "Crash dumps to multiple vdev pools.", B_FALSE, B_FALSE,
              B_FALSE, NULL);
--- 168,178 ----
              B_FALSE, NULL);
  
          zfeature_register(SPA_FEATURE_LZ4_COMPRESS,
              "org.illumos:lz4_compress", "lz4_compress",
              "LZ4 compression algorithm support.", B_FALSE, B_FALSE,
!             B_TRUE, NULL);
  
          zfeature_register(SPA_FEATURE_MULTI_VDEV_CRASH_DUMP,
              "com.joyent:multi_vdev_crash_dump", "multi_vdev_crash_dump",
              "Crash dumps to multiple vdev pools.", B_FALSE, B_FALSE,
              B_FALSE, NULL);