Fix build on older Macs

In commit 39ffb0fced85 ("Fix Subsurface build with Qt 5.4.1 and later") Thiago
was a bit too aggressive removing some of our ifdefs for building with older
versions of the SDK...

I need at least this patch to still build on the machine that I use to create
the official binaries.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

subsurfacesysinfo.cpp

@@ -551,7 +551,11 @@ QString SubsurfaceSysInfo::prettyProductName()
 	case MV_MAVERICKS:
 		basename = "OS X Mavericks (";
 		break;
+#ifdef MV_YOSEMITE
 	case MV_YOSEMITE:
+#else
+	case 0x000C: // MV_YOSEMITE
+#endif
 		basename = "OS X Yosemite (";
 		break;
 	}