[libcutil] Suppress debug info to STDOUT

[mocchira]

Now leo_gateway dumps kind of the below content into erlang.log during the start up

slab class   1: chunk size       264 perslab   31775
slab class   2: chunk size       528 perslab   15887
slab class   3: chunk size      1056 perslab    7943
slab class   4: chunk size      2112 perslab    3971
slab class   5: chunk size      4224 perslab    1985
slab class   6: chunk size      8448 perslab     992
slab class   7: chunk size     16896 perslab     496
slab class   8: chunk size     33792 perslab     248
slab class   9: chunk size     67584 perslab     124
slab class  10: chunk size    135168 perslab      62
slab class  11: chunk size    270336 perslab      31
slab class  12: chunk size    540672 perslab      15
slab class  13: chunk size   1081344 perslab       7
slab class  14: chunk size   2162688 perslab       3
slab class  15: chunk size   8388608 perslab       1
ps:0x7ff1a401c570

this should be suppressed as it's mainly debug purpose output.

[mocchira]

leo-project/libcutil#6 fixed this issue so I'll close.