Android: Don't register main thread on loading library

When building with debug, all SLOT or SIGNAL macros will
expand to a function call, and then function will call
QThreadData::current(), which will set
QCoreApplication::theMainThread if it has not already been
done. Since Qt Widgets has these macros in the static
initialization of the library, we would register the
Android main thread as the main thread of Qt, which would
mean that the actual application object was created on
a different thread than the main thread. This caused warnings
to appear, and also triggered a race condition which
caused widget applications to sometimes show a black screen
instead of content on startup when run with the OpenGL plugin.

Task-number: QTBUG-35048
Change-Id: Ie8979f5e7cd5662f8d7dd276de9f94f27cc120b5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
eglfs: Allow using a different framebuffer device

Right now /dev/fb0 is hardcoded. This is not ideal. Therefore
QT_QPA_EGLFS_FB is introduced. This environment variable can be set to
a different framebuffer device. Once it is set, eglfs will use the
specific device. This is similar to linuxfb's fb=... plugin parameter.

The actual behavior depends on the board-specific implementations.
For now only iMX6 has real support. It extracts the index from the
device name as bind the EGL display to the corresponding framebuffer
using the vendor-specific fbGetDisplayByIndex(). Other hooks can
follow suit later on.

With this patch eglfs is at least on par with linuxfb, meaning that,
if the board supports it, different apps can run on different screens.

Task-number: QTBUG-36113
Change-Id: Ia3c88bd06e108bc668433e3c5c3fce34a5a0e73d
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Do not consider a signal to be connected if only a signal spy is installed.

This fixes QtQuick key handling not propagating key events beyond the
specific onXPressed handlers, due to erroneously thinking those exist,
when signal spy callbacks are present.

Considering signal spies for isSignalConnected() goes back to 87239ef6 in
Qt4, and seems to be there just due to this code being based on activate(),
where this check obviously makes sense.

Change-Id: Iad41e42a8d3ee2a16a55be7d1a7cdc51484981ce
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
test: Don't build qmimedatabase-cache for QNX

update-mime-database does not exist, so there is no point in
trying to build this test.

Change-Id: Id60f2f8fc3af33d3f7ae2fb4f1042356b60f6596
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Wolfgang Bremer <wbremer@blackberry.com>