conform wrapper symbol to ISC style. include isc/result.h for isc_result_t.

lib/tests/include/tests/t_api.h

@@ -15,11 +15,13 @@
  * SOFTWARE.
  */
 
-#ifndef ISC_T_API_H
-#define ISC_T_API_H 1
+#ifndef TESTS_T_API_H
+#define TESTS_T_API_H 1
 
 #include <stdio.h>
 
+#include <isc/result.h>
+
 /*
  *
  * Result codes.
@@ -85,5 +87,5 @@ t_bustline(char *line, char **toks);
 int
 t_eval(char *filename, int (*func)(char **), int nargs);
 
-#endif /* ISC_T_API_H */
+#endif /* TESTS_T_API_H */