Thanks for the explanation; I installed the attached further patch.
>From 6ff8421cf8709b1c210b6a15118d3baa2d6685a8 Mon Sep 17 00:00:00 2001
From: Paul Eggert
Date: Sun, 16 Apr 2017 12:43:20 -0700
Subject: [PATCH] regex: port better to Solaris 10
Solaris 10 includes , which #defines
gettext, and this causes a double #define.
Problem reported by Gavin Smith in:
http://lists.gnu.org/archive/html/bug-gnulib/2017-04/msg00056.html
* lib/regex_internal.h (gettext): #undef before #defining.
---
ChangeLog| 9 +
lib/regex_internal.h | 1 +
2 files changed, 10 insertions(+)
diff --git a/ChangeLog b/ChangeLog
index b19910b..f57c376 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2017-04-16 Paul Eggert
+
+ regex: port better to Solaris 10
+ Solaris 10 includes , which #defines
+ gettext, and this causes a double #define.
+ Problem reported by Gavin Smith in:
+ http://lists.gnu.org/archive/html/bug-gnulib/2017-04/msg00056.html
+ * lib/regex_internal.h (gettext): #undef before #defining.
+
2017-04-15 Paul Eggert
intprops: improve comments
diff --git a/lib/regex_internal.h b/lib/regex_internal.h
index 9bb0740..8270207 100644
--- a/lib/regex_internal.h
+++ b/lib/regex_internal.h
@@ -102,6 +102,7 @@
__dcgettext (_libc_intl_domainname, msgid, LC_MESSAGES)
# endif
#else
+# undef gettext
# define gettext(msgid) (msgid)
#endif
--
2.7.4