work around MSVC2010 ICE

Task-number: QTBUG-42064
Change-Id: Ifffcc0cf9109b76d79f603a13792d7fd9979761c
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

qmake/library/proitems.cpp

@@ -416,8 +416,8 @@ QStringList ProStringList::toQStringList() const
 {
     QStringList ret;
     ret.reserve(size());
-    foreach (const ProString &str, *this)
-        ret << str.toQString();
+    for (int i = 0; i < size(); i++) // foreach causes MSVC2010 ICE
+        ret << at(i).toQString();
     return ret;
 }