Mem obj trans

[VadimZhestikov]

Memory consumption fixes.

Test results for following test:

function init(size) {
    var o = {};
    for (var i=0; i<size; i++) {
        o[`some_property${i}`] = i;
    }
}

function handler() {
    var size = ("undefined" == typeof scriptArgs) ? Number(process.argv[2]):
       Number(scriptArgs[1]);

    console.log('init size='+size);

    init(size);
}

handler();

############### test-fill-array 1000000

qjs
init size=1000000
        0:00.36 real,   0.34 user,      0.04 sys        RSS:91584kb

njs (this patch)
init size=1000000
        0:00.46 real,   0.33 user,      0.12 sys        RSS:137480kb

njs (before this patch)
init size=1000000
        0:00.94 real,   0.51 user,      0.42 sys        RSS:607656kb

njs v0.8.9 (before "atomic patch")
init size=1000000
        0:00.58 real,   0.38 user,      0.19 sys        RSS:500096kb

############### bench4

qjs
Richards: 896
Crypto: 1070
RayTrace: 988
NavierStokes: 2021
----
Score (version 9): 1176
RSS:6424kb

njs (this patch)
Richards: 590
Crypto: 1008
RayTrace: 421
NavierStokes: 1475
----
Score (version 9): 779
RSS:2103936kb

njs (before this patch)
Richards: 634
Crypto: 985
RayTrace: 505
NavierStokes: 1495
----
Score (version 9): 828
RSS:2710656kb

njs v0.8.9 (before "atomic patch")
Richards: 375
Crypto: 725
RayTrace: 360
NavierStokes: 1345
----
Score (version 9): 602
RSS:2802944kb

[VadimZhestikov]

Just updated by commits from #935

[xeioex]

LGTM.