Don't crash if the relayed signal was emitted from the wrong thread

Under normal circumstances, this should never happen. Signals exported
to D-Bus should only be emitted from the object's own thread. That's the
only way for the receiver (the QDBusAdaptorConnector object) to know
what the sender object and signal were. If they are emitted from another
thread, the sender will be null.

Task-number: QTBUG-31932
Change-Id: Ia5a45d648985e0645bffd4abc0881fca9da64f79
Reviewed-by: Lorn Potter <lorn.potter@jollamobile.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Fix change-of-sign warning found by ICC

qstring.cpp(3896): error #68: integer conversion resulted in a change of sign

The line before also had 0x8000, but since there was no addition,
0x8000 was a literal converted to short. However, 0xff + 0x8000 is an
int, and 0x80ff is positive, while short(0x80ff) is negative.

Change-Id: I445ff401d817b643479e54320525890ce12bbfe5
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Don't enable EGL support if OpenGL is disabled.

QtPlatformSupport fails to build if EGL support is enabled but OpenGL
isn't. It tries to compile eglconvenience, but qplatformopenglcontext.h
is empty (#ifndef QT_NO_OPENGL).

It makes no sense to have EGL with no OpenGL ES, so make sure we don't
try it.

The current test to disable EGL if OpenGL desktop is active is upside
down. With -opengl desktop -no-egl, it would complain that EGL support
was requested.

Task-number: QTBUG-28763
Change-Id: I80c780ec78181f3fa85f43e41be21d1217d76610
Reviewed-by: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>