Don't cache mapping between source and private header

When switching from a header to a source file, the source->header
mapping is cached. It's not the case anymore for private headers (_p).

Change-Id: I481c0613e29db0a3fb4e17f339626abb49ffa8e2
Reviewed-by: Leandro Melo <leandro.melo@nokia.com>

src/plugins/cpptools/cpptoolsplugin.cpp

@@ -294,7 +294,8 @@ QString CppToolsPlugin::correspondingHeaderOrSourceI(const QString &fileName) co
         const QFileInfo candidateFi(absoluteDir, candidateFileName);
         if (candidateFi.isFile()) {
             m_headerSourceMapping[fi.absoluteFilePath()] = candidateFi.absoluteFilePath();
-            m_headerSourceMapping[candidateFi.absoluteFilePath()] = fi.absoluteFilePath();
+            if (type != HeaderFile || !baseName.endsWith(privateHeaderSuffix))
+                m_headerSourceMapping[candidateFi.absoluteFilePath()] = fi.absoluteFilePath();
             return candidateFi.absoluteFilePath();
         }
     }