WinRT: Fix compilation after ANGLE update

Header inclusion is not needed, hence remove it for WinRT.

Change-Id: I8117439849143975cad3dc14e36118b8da4621de
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>
Fix bogus videonode plugin handling

Each plugin must provide its own unique key. Otherwise we will only ever
see one single plugin.

Right now running on i.MX6 is often broken because the imx6 videonode plugin is
not picked up since only the egl one is seen by the system. With the fix both plugins
provide their own unique key so both become visible.

Additionally, introduce a QT_VIDEONODE environment variable. This is useful to specify
which plugin to use. This is necessary in case multiple custom videonode plugins support
the same formats.

Change-Id: Iaa1988f8436dcb938cb9a95e2e0d68a4e92e113c
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>
Merge remote-tracking branch 'origin/5.4.0' into 5.4

Change-Id: Iec2c793710c95919975aa3c03144d915ca5fa84f
Fix Clang warning about comparison of different signs

Commit 4d35f66acf90e64e6c174bee9d809713d07fcd7e changed from -1 to ~0 because
ICC complained, but Clang still sees ~0 as int. So force to unsigned.

qgstappsrc.cpp:144:31: warning: comparison of integers of different signs: 'unsigned int' and 'int' [-Wsign-compare]

Change-Id: I6b0fdf8dc5df157d8e184f22dba44660e60ca3b2
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>
Remove unused private members

One is not used, the others are not even initialized, so don't use the
memory.

qsoundeffect_pulse_p.h:172:20: warning: private field 'm_resourceStatus' is not used [-Wunused-private-field]
qvideowidget_p.h:211:25: warning: private field 'm_aspectRatioMode' is not used [-Wunused-private-field]
qalsaaudioinput.h:156:22: warning: private field 'timestamp' is not used [-Wunused-private-field]
qalsaaudiooutput.h:135:22: warning: private field 'timestamp' is not used [-Wunused-private-field]

Change-Id: I7c9f50d57c4d29ee0dfd7dc086771d721cdb5b05
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>