Avoid compiler warning about alignment for MSVC2013 (x64)

Only align if we actually *need to* (due to SSE/XOP usage)

The code will currently not compile as it is now with UseSSE or
UseXOP defined, (so the ALIGN macro could just
be totally removed). In order to keep the diff to upstream as small
as possible, we keep the ALIGN macro definition.

Task-number: QTBUG-34362
Change-Id: I6cf420205896e3a476cdcfbf3308a07e0ae0c84e
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
QFormLayout: Avoid assertion with negative spacings.

It's not really clear if styles *must* return a non-negative value for
QStyle::pixelMetric(PM_Layout{Vertical,Horizontal}Spacing), but both
QBoxLayout and QGridLayout seems to be robust enough to handle this.
They will simply make sure that the spacing is never negative.
We therefore make QFormLayout equally robust.

Task-number: QTBUG-34731

Change-Id: I62235bfcd8adf7757cf15bc9927b29650ae6459d
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>