Rename to QArrayData::ArrayOptions in preparation for these flags
being in the array itself, instead of used just for allocating new
ones.
For that reason, rename QArrayData::Default to
DefaultAllocationFlags. And introduce QArray::DefaultRawFlags to mean
the flags needed for creating a raw (static) QArrayData.
Also rename QArrayData::Grow to GrowsForward, so we may add
GrowsBackward in the future.
Change-Id: I536d9b34124f775d53cf810f62d6b0eaada8daef
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>