Add minimal strsignal for platforms without it.

configure.ac

@@ -1770,6 +1770,7 @@ AC_CHECK_FUNCS([ \
 	strnlen \
 	strnvis \
 	strptime \
+	strsignal \
 	strtonum \
 	strtoll \
 	strtoul \

openbsd-compat/bsd-misc.c

@@ -104,6 +104,16 @@ const char *strerror(int e)
 }
 #endif
 
+#if !defined(HAVE_STRSIGNAL)
+char *strsignal(int sig)
+{
+	static char buf[16];
+
+	(void)snprintf(buf, sizeof(buf), "%d", sig);
+	return buf;
+}
+#endif
+
 #ifndef HAVE_UTIMES
 int utimes(char *filename, struct timeval *tvp)
 {

openbsd-compat/bsd-misc.h

@@ -49,6 +49,10 @@ int setegid(uid_t);
 const char *strerror(int);
 #endif
 
+#if !defined(HAVE_STRSIGNAL)
+char *strsignal(int);
+#endif
+
 #if !defined(HAVE_SETLINEBUF)
 #define setlinebuf(a)	(setvbuf((a), NULL, _IOLBF, 0))
 #endif