Rename .h header files to .hpp

Majority of the project uses .hpp and .h shouldn't be used for C++
header files anyway.

Change-Id: I979ba2d243f8f5dbf45c37237ac4aaf9a733eba8
diff --git a/tests/datastoreaccess_mock.hpp b/tests/datastoreaccess_mock.hpp
index 289d919..e9dc870 100644
--- a/tests/datastoreaccess_mock.hpp
+++ b/tests/datastoreaccess_mock.hpp
@@ -7,7 +7,7 @@
 
 #include <map>
 #include "datastore_access.hpp"
-#include "trompeloeil_doctest.h"
+#include "trompeloeil_doctest.hpp"
 #include "utils.hpp"
 
 namespace trompeloeil {