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/enum_completion.cpp b/tests/enum_completion.cpp
index c6b31d8..939243f 100644
--- a/tests/enum_completion.cpp
+++ b/tests/enum_completion.cpp
@@ -7,7 +7,7 @@
  *
  */
 
-#include "trompeloeil_doctest.h"
+#include "trompeloeil_doctest.hpp"
 #include "datastoreaccess_mock.hpp"
 #include "parser.hpp"
 #include "pretty_printers.hpp"