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

*** 241,257 ****
  \fBlzjb\fR. It is also approximately 80% faster on decompression, while
  giving approximately 10% better compression ratio.
  
  When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
  administrator can turn on \fBlz4\fR compression on any dataset on the
! pool using the \fBzfs\fR(1M) command. Please note that doing so will
! immediately activate the \fBlz4_compress\fR feature on the underlying
! pool (even before any data is written), and the feature will not be
! deactivated. Since this feature is not read-only compatible, this
! operation will render the pool unimportable on systems without support
! for the \fBlz4_compress\fR feature. Booting off of \fBlz4\fR-compressed
! root pools is supported.
  .RE
  
  .sp
  .ne 2
  .na
--- 241,258 ----
  \fBlzjb\fR. It is also approximately 80% faster on decompression, while
  giving approximately 10% better compression ratio.
  
  When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
  administrator can turn on \fBlz4\fR compression on any dataset on the
! pool using the \fBzfs\fR(1M) command. Also, all newly written metadata
! will be compressed with \fBlz4\fR algorithm. Since this feature is not
! read-only compatible, this operation will render the pool unimportable
! on systems without support for the \fBlz4_compress\fR feature. Booting
! off of \fBlz4\fR-compressed root pools is supported.
! 
! This feature becomes \fBactive\fR as soon as it is enabled and will
! never return to being \fBenabled\fB.
  .RE
  
  .sp
  .ne 2
  .na