Fix display of MSVC2015 in compilerString().

Display values of _MSC_VER >= 1900 (currently displayed as MSVC 2014)
as MSVC2015 and larger values as unknown.

Change-Id: Id23b0f9342e6ad6d776bb44743e5e4ce91462c8f
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/coreplugin/icore.cpp

@@ -464,6 +464,10 @@ static QString compilerString()
 #elif defined(Q_CC_GNU)
     return QLatin1String("GCC " ) + QLatin1String(__VERSION__);
 #elif defined(Q_CC_MSVC)
+    if (_MSC_VER > 1999)
+        return QLatin1String("MSVC <unknown>");
+    if (_MSC_VER >= 1900) // 1900: MSVC 2015
+        return QLatin1String("MSVC 2015");
     if (_MSC_VER >= 1800) // 1800: MSVC 2013 (yearly release cycle)
         return QLatin1String("MSVC ") + QString::number(2008 + ((_MSC_VER / 100) - 13));
     if (_MSC_VER >= 1500) // 1500: MSVC 2008, 1600: MSVC 2010, ... (2-year release cycle)