Rename QMetaType::construct() to create()

Rename QMetaType::construct() to create()

create() is symmetric with destroy().

Also rename the internal methods and fields to be
consistent (qDeleteHelper already had the "right"
name, though!).

This change will allow us to use construct() and
destruct() for something else: Placement new-style
allocation (QTBUG-12574).

The old construct() is still kept for now, until
the other repositories have been updated to use
create().

Change-Id: Iceb184af6cffcb0a634359cfc3516c718ba0c2f5
Reviewed-on: http://codereview.qt-project.org/6342
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>