Add missing GETTEXT_FLAGS entry

Author: petere

src/bin/psql/nls.mk

@@ -11,4 +11,5 @@ GETTEXT_FILES    = $(FRONTEND_COMMON_GETTEXT_FILES) \
                    ../../common/wait_error.c ../../port/thread.c
 GETTEXT_TRIGGERS = $(FRONTEND_COMMON_GETTEXT_TRIGGERS) \
                    HELP0 HELPN N_ simple_prompt simple_prompt_extended
-GETTEXT_FLAGS    = $(FRONTEND_COMMON_GETTEXT_FLAGS)
+GETTEXT_FLAGS    = $(FRONTEND_COMMON_GETTEXT_FLAGS) \
+                   HELPN:1:c-format