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/leaf_editing.cpp b/tests/leaf_editing.cpp
index 61704f6..655f269 100644
--- a/tests/leaf_editing.cpp
+++ b/tests/leaf_editing.cpp
@@ -6,7 +6,7 @@
  *
 */
 
-#include "trompeloeil_doctest.h"
+#include "trompeloeil_doctest.hpp"
 #include <boost/core/demangle.hpp>
 #include "ast_commands.hpp"
 #include "parser.hpp"