Merge from gnulib.

This incorporates:
2013-06-02 sig2str: port to C++
2013-05-29 c-ctype, regex, verify: port to gcc -std=c90 -pedantic

ChangeLog

+2013-06-09  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Merge from gnulib, incorporating:
+	2013-06-02 sig2str: port to C++
+	2013-05-29 c-ctype, regex, verify: port to gcc -std=c90 -pedantic
+
 2013-06-08  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* configure.ac (HAVE_GLIB): Only set XGSELOBJ if HAVE_NS = no.

lib/c-ctype.h

@@ -136,7 +136,8 @@ extern int c_tolower (int c) _GL_ATTRIBUTE_CONST;
 extern int c_toupper (int c) _GL_ATTRIBUTE_CONST;
 
 
-#if defined __GNUC__ && defined __OPTIMIZE__ && !defined __OPTIMIZE_SIZE__ && !defined NO_C_CTYPE_MACROS
+#if (defined __GNUC__ && !defined __STRICT_ANSI__ && defined __OPTIMIZE__ \
+     && !defined __OPTIMIZE_SIZE__ && !defined NO_C_CTYPE_MACROS)
 
 /* ASCII optimizations. */
 

lib/sig2str.h

@@ -27,9 +27,17 @@
 /* Size of a buffer needed to hold a signal name like "HUP".  */
 # define SIG2STR_MAX (sizeof "SIGRTMAX" + INT_STRLEN_BOUND (int) - 1)
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 int sig2str (int, char *);
 int str2sig (char const *, int *);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
 
 /* An upper bound on signal numbers allowed by the system.  */

lib/verify.h

@@ -31,7 +31,9 @@
    Use this only with GCC.  If we were willing to slow 'configure'
    down we could also use it with other compilers, but since this
    affects only the quality of diagnostics, why bother?  */
-# if (4 < __GNUC__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus
+# if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \
+      && (201112L <= __STDC_VERSION__  || !defined __STRICT_ANSI__) \
+      && !defined __cplusplus)
 #  define _GL_HAVE__STATIC_ASSERT 1
 # endif
 /* The condition (99 < __GNUC__) is temporary, until we know about the