QDateTime: future-proof swap()

In Qt 7 32-bit builds, the ShortData will be larger than the
d-pointer.

So don't swap() the d-pointer, but a) delegate to Data to swap itself
and b) swap the ShortData there, adding a static_assert in the .cpp
file that triggers when the assumption that ShortData is always at
least as large as a pointer is violated.

Found while porting away from overly-generic qSwap(), so done that,
too.

Task-number: QTBUG-97601
Pick-to: 6.3 6.2
Change-Id: I5139da58d99e9491a582ff2cb2f817cd96952044
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions