qRound64 does not round correctly for very large integers

The following code fails with the message below:

qlonglong i64 = (1ll << 52) + 1;
double d = i64;
QVERIFY(d == i64);
QCOMPARE(qRound64(d), i64);

FAIL! Compared values are not the same
Actual (qRound64(d)): 4503599627370498
Expected (i64) : 4503599627370497

The integer value above has an exact representation within a double. It is the qRound64 method, which adds 0.5 to the integral value and thus introduces loss of precision in this step.

I didn't check if qRound is affected as well.