buildroot

qt5webengine: enable build for 5.6.3

The build was broken in 5.6.2 and was disabled.

It compiles fine since 5.6.3.

The two additional patches are useful at run-time.

The first one avoid the need to specify the path to the SSL certificate
directory (using an additional environment variable).

The second one is the same used in 5.9.x (plus resolved conflicts). It uses the
process's context to get handles on EGL and GLESv2 libraries. Those libraries
are linked to Qt WebEngine at compile time.

The patch is particularly usefull for RPI boards since the raspberrypi userland
package does not provide the libEGLv2.so.2 and libGLES.so.1 symlinks. Both
library paths are hardcoded in Qt WebEngine.

Signed-off-by: Gaël PORTAY <gael.portay@savoirfairelinux.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>