Let the compiler do the unaligned loads in QBitArray::count(bool)

For platforms where the CPU can do unaligned loads on its own, like
x86, the compiler will generate actual loads. On other CPUs, it will
do the byte-by-byte load like we were doing. The compiler cannot
generate worse code than our hand-rolled load, so this change can only
improve performance.

Change-Id: I32a89e64aa64d8af504be6c5a10b04d7573cdb98
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Do 64-bit loops in QBitArray::count(bool)

On 64-bit platforms, with unaligned loads, this is defintely an
improvement since we can run fewer instructions. On 32-bit platforms
with unaligned loads, we'll do the exact same number of loads. On
platforms without unaligned loads, it's no worse.

Change-Id: Idd5dd5213975d77bbc3adf486adbf6f8ef071341
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Use Q_STATIC_ASSERT to report error about missing Q_OBJECT

Q_STATIC_ASSERT gives better error with C++11 enabled.

Aslo the qt_check_for_QOBJECT_macro had warning on some compiler since
it used null reference

Change-Id: Ic6115da800064b00c50a5762f0b79f5f656bf750
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>