replace #if HAVE_CONFIG_H by #ifdef HAVE_CONFIG_H

it seems like most build systems pass a -DHAVE_CONFIG_H flag to the
compiler which still causes `#if HAVE_CONFIG_H` to be false while it
clearly is supposed to be triggered.

That said, I do not really see a good reason why the inclusion of the
`config.h` file should be guarded in the first place: the file is
guaranteed to always available by proper build systems, and if it was
not included the build either breaks at the linking stage or -- at the
very least -- the runtime behavior of the resulting libraries will be
very awkward.

examples/flow_legacy.cpp

@@ -20,7 +20,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_mpi.cpp

@@ -20,7 +20,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_multisegment.cpp

@@ -20,7 +20,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_multisegment_mpi.cpp

@@ -20,7 +20,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_polymer.cpp

@@ -19,7 +19,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_reorder.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_sequential.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/flow_solvent.cpp

@@ -20,7 +20,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/sim_2p_comp_reorder.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/sim_2p_incomp.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/sim_2p_incomp_ad.cpp

@@ -19,7 +19,7 @@
 
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/sim_poly2p_comp_reorder.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

examples/sim_poly2p_incomp_reorder.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/autodiff/SimulatorIncompTwophaseAd.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/polymer/SimulatorCompressiblePolymer.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/polymer/SimulatorPolymer.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/simulators/SimulatorCompressibleTwophase.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/simulators/SimulatorIncompTwophase.cpp

@@ -17,7 +17,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

opm/simulators/WellSwitchingLogger.cpp

@@ -18,7 +18,7 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H
 

tests/test_singlecellsolves.cpp

@@ -18,7 +18,7 @@
 */
 
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif // HAVE_CONFIG_H