Reintroduce -geometry command line argument for X11/XCB.

Add parsing for the window geometry specification to
QGuiApplicationPrivate. Enable the argument under a different
name for the other platforms as well.

Task-number: QTBUG-27349
Change-Id: I973b2c69f5172f7d0bc983b8ba4b0d164649ef02
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
XCB: Readd support for -name command line argument.

Task-number: QTBUG-27349

Change-Id: I85390942927cd1c54f76fd7ddc0f3487c7205b57
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>