include all module dependencies into pkg-config Requires: field

previously, we'd miss the -private ones (which imply the non-private
version).

Change-Id: Ib5ae2afaa5b5efda9639b7cc4a080432f2fcce2a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Dihan Wickremasuriya <nayomal@gmail.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

mkspecs/features/qt_module.prf

@@ -206,7 +206,7 @@ unix {
 }
 
 unix|win32-g++* {
-    for(i, QT): \
+    for(i, MODULE_DEPENDS): \
         QMAKE_PKGCONFIG_REQUIRES += $$replace(QT.$${i}.name, ^Qt, Qt$$eval(QT.$${i}.MAJOR_VERSION))
     isEmpty(QMAKE_PKGCONFIG_DESCRIPTION): \
         QMAKE_PKGCONFIG_DESCRIPTION = $$replace(TARGET, ^Qt, "Qt ") module