actively try to obtain PID of non-pthread inferiors with gdb < 7 on linux

Reviewed-by: hjk

src/plugins/debugger/gdb/gdbengine.h

@@ -302,6 +302,8 @@ private: ////////// Inferior Management //////////
     void maybeHandleInferiorPidChanged(const QString &pid);
 
 #ifdef Q_OS_LINUX
+    void handleInfoProc(const GdbResponse &response);
+
     QByteArray m_entryPoint;
 #endif