(partially) Fix Bug#55227 Fix compiler warnings in innodb with gcc 4.6

Fix compiler warning:
log/log0recv.c: In function 'recv_synchronize_groups':
log/log0recv.c:562:14: error: variable 'limit_lsn' set but not used [-Werror=unused-but-set-variable]

storage/innodb_plugin/log/log0recv.c

@@ -559,10 +559,8 @@ recv_synchronize_groups(
 	ib_uint64_t	start_lsn;
 	ib_uint64_t	end_lsn;
 	ib_uint64_t	recovered_lsn;
-	ib_uint64_t	limit_lsn;
 
 	recovered_lsn = recv_sys->recovered_lsn;
-	limit_lsn = recv_sys->limit_lsn;
 
 	/* Read the last recovered log block to the recovery system buffer:
 	the block is always incomplete */