Add some basic debug output for log compression

Guarded by --debug=compress, like the other debug measures.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/README b/README
index 457b83d..e378d3b 100644
--- a/README
+++ b/README
@@ -210,6 +210,7 @@
 	time		Dump info related to internal time keeping
 	net		Dump info related to networking connections
 	rate		Dump info related to IO rate switching
+	compress	Dump info related to log compress/decompress
 	? or help	Show available debug options.
 
 One can specify multiple debug options: e.g. --debug=file,mem will enable