Method overwrite

test/testchunks.cpp:58–64

}

void TestChunks::overwrite(qint64 pos, char b)
{
    _data[(int)pos] = b;
    _highlighted[(int)pos] = 1;
    _chunks.overwrite(pos, b);
    compare();
}

void TestChunks::removeAt(qint64 pos)
{