Revert "package/qt5webkit-examples: remove obsolete package"

Revert "package/qt5webkit-examples: remove obsolete package"

This reverts commit 940bfe2f4336a3fea1ec6805db1f90ce83bd4a78 with the
following changes:

 - new hashes for 5.6.3 and 5.9.1 (there is no 5.9.2).
 - BR2_PACKAGE_QT5BASE_LICENSE_APPROVED has been removed
 - add GPL-3 to licences
 - uses SPDX identifier for licences
 - add missing dependencies (qt5base, qt5webkit, qt5declarative)
 - removes /usr when qmake host-tools is invoked at configure

Signed-off-by: Gaël PORTAY <gael.portay@savoirfairelinux.com>
[Thomas: add entry in the DEVELOPERS file.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>