Bugfix: Restore old behaviour of USE_UPNP as close as possible (built & enabled by default, can be disabled or unsupported by option)

bitcoin-qt.pro

@@ -16,10 +16,17 @@ OBJECTS_DIR = build
 MOC_DIR = build
 UI_DIR = build
 
-# use: qmake "USE_UPNP=0" (disable by default) or "USE_UPNP=1" (enable by default)
-# miniupnpc (http://miniupnp.free.fr/files/) must be installed
-count(USE_UPNP, 1) {
+# use: qmake "USE_UPNP=1" ( enabled by default; default)
+#  or: qmake "USE_UPNP=0" (disabled by default)
+#  or: qmake "USE_UPNP=-" (not supported)
+# miniupnpc (http://miniupnp.free.fr/files/) must be installed for support
+contains(USE_UPNP, -) {
+    message(Building without UPNP support)
+} else {
     message(Building with UPNP support)
+    count(USE_UPNP, 0) {
+        USE_UPNP=1
+    }
     DEFINES += USE_UPNP=$$USE_UPNP
     LIBS += -lminiupnpc
 }