patch 9.1.0570: tests: test_gettext_make can be improved

Problem:  tests: test_gettext_make can be improved
          (after v9.1.0559)
Solution: Improve the test
          (Ken Takata)

* Remove unnecessary comment.
* Check the gettext feature.
* Check whether %GETTEXT_PATH% is set.
* Check the return code of the make command.
* Use heredoc.

closes: #15221

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 4c6ed99..2003f53 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    570,
+/**/
     569,
 /**/
     568,