Fix ‘looses precision’ warning in public API

Change-Id: I935e6f278e539f8e6aaca0bc381371ec85aa5c67
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
XCB: Don't recalculate the DPI if we have a forced DPI setting

logicalDpi() already has the logic to check m_forcedDpi, so let's reuse
it. I hope it's not a problem that we send a signal that it changed when
nothing changed.

[ChangeLog][Platform Specific Changes][X11 / XCB]Fixed a bug that caused
Qt applications to think the screen DPI had changed when it had not,
after connecting or disconnecting monitors.

Task-number: QTBUG-32683
Change-Id: I45dd27de5109e65e7599915f11cfdb633a65a67c
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
xcb: added env variables to show input devices and events

export QT_XCB_DEBUG_XINPUT_DEVICES=anything to show detected
input devices at startup
export QT_XCB_DEBUG_XINPUT=anything to log mouse, touch and tablet events

Change-Id: Id14844b68ad376740f82a36aab2c59c84d2017ab
Task-number: QTBUG-35583
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
fix compile of qt without egl available

move the dpy to the place where it is used inside the egl ifdef guard
fixes compilation on old distros not having egl

Change-Id: I7eebe5305f3a584c0c5da2ea7b9099fdd994249d
Reviewed-by: David Faure <david.faure@kdab.com>