Fix warnings on qt5/osx build slave.
Try to fix compiler warnings on OSX/clang:

warning: cast from 'quint8 *' (aka 'unsigned char *') to 'quint32 *'
(aka 'unsigned int *') increases required alignment from 1 to 4
[-Wcast-align]

and

warning: cast from 'quint8 *' (aka 'unsigned char *') to 'quint64 *'
(aka 'unsigned long long *') increases required alignment from 1
to 8 [-Wcast-align]

By using explicit C++-style casts (reinterpret_cast) instead of
implicit C-style casts we can quench this warning.