Do not force a content-type on POST request with no content

While a POST request with no body may be a pointless thing it does
happen on many websites. Currently this causes QtNetwork to print a
warning to the console and set an invalid content-type. This patch
allows the content-type to be absent when content is.

Task-number: QTBUG-42479
Change-Id: Ia84c89147d2469a9421b9694d062c797987b3194
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Add a note about group separators to numeric validators.

Task-number: QTBUG-42522
Change-Id: I202cb98c51ba2332000772edfdc47d47c56e49c9
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Fix invalid qmake syntax

Task-number: QTBUG-42549
Change-Id: I57ba3150e3a3b915faf0356d8a3f89801eb4963e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@theqtcompany.com>
Fix rubberband position for tabbed mdi windows

Place the rubberband over the tabs instead of where the hidden
subwindows happen to be.

[ChangeLog][QtWidgets][QMdiArea] Fix rubberband position for tabbed mdi windows

Task-number: QTBUG-42612
Change-Id: I41e81ab8b99ab9e0fa533fd4ed1b2a8141d19753
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Doc: added NoGesture to GestureState enum

Task-number: QTBUG-39988
Change-Id: I5481dfec75c90267a3a9be0d212df7384016e69d
Reviewed-by: Martin Smith <martin.smith@digia.com>