Fix compilation of qserialport auto-test with Qt4

1. The QCOMPARE macro can not make type cast between "int" and
"qint64", though on qt5 there are no problems.

2. The QSKIP macro should accept two input parameters.

Tested build on Lixux 64bit and Windows with Qt4 and then Qt5.

Change-Id: I1f8497201e8d704098faea789bc61829f0d2f9e4
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>