support cleanly querying private modules in qtHaveModule()

module names use dashes, but the internal module representation uses
underscores, so we must translate.

Change-Id: Ib6983d3731e7dae2a4d6232f8a5202390fd425e9
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

mkspecs/features/qt_functions.prf

@@ -48,7 +48,7 @@ defineTest(qtProcessModuleFlags) {
 
 # qt module
 defineTest(qtHaveModule) {
-    !isEmpty(QT.$${1}.name): \
+    !isEmpty(QT.$$replace(1, -, _).name): \
         return(true)
     return(false)
 }