Fixed compile of quicktime plugin

This code was including the qmacdefines_mac.h header from QtWidgets,
which has recently been removed.  Using the header is no longer
necessary.

Note that the qmacdefines_mac.h contained a workaround for some mac
system headers declaring variables named `slots'.  Replace that
workaround with the standard no_keywords method.

Change-Id: Icd47a562d64953692e50a9fea8bb4a9c8424375c
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/qt7/qt7.pro

@@ -1,5 +1,8 @@
 load(qt_module)
 
+# Avoid clash with a variable named `slots' in a Quartz header
+CONFIG += no_keywords
+
 TARGET = qqt7engine
 QT += multimedia-private network
 !isEmpty(QT.widgets.name) {