Make sure that sign extension does not happen when we convert to wide

characters. From Miloslav Trmac

regress/lib/libc/citrus/mbtowc/Makefile

@@ -0,0 +1,16 @@
+#	$NetBSD: Makefile,v 1.1 2005/03/27 18:49:51 christos Exp $
+
+NOMAN=		# defined
+
+PROG=		mbtowc_test
+WARNS?=		1
+
+regress: ${PROG}
+	@if ./${PROG}; then \
+		echo PASSED; \
+	else \
+		echo FAILED; \
+		exit 1; \
+	fi
+
+.include <bsd.prog.mk>

regress/lib/libc/citrus/mbtowc/mbtowc_test.c

@@ -0,0 +1,30 @@
+/* From: Miloslav Trmac <mitr@volny.cz> */
+#include <langinfo.h>
+#include <limits.h>
+#include <locale.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int
+main(void)
+{
+	wchar_t wc;
+	char back[MB_LEN_MAX];
+	int ret;
+	size_t i;
+
+	setlocale(LC_ALL, "");
+	printf("Charset: %s\n", nl_langinfo(CODESET));
+	ret = mbtowc(&wc, "\xe4", 1);
+	printf("mbtowc(): %d\n", ret);
+	if(ret > 0) {
+		printf("Result: 0x%08lX\n",(unsigned long)wc);
+		ret = wctomb(back, wc);
+		printf("wctomb(): %d\n", ret);
+		for(i = 0; ret > 0 && i <(size_t)ret; i++)
+			printf("%02X ",(unsigned char)back[i]);
+		putchar('\n');
+		return EXIT_SUCCESS;
+	} else
+		return EXIT_FAILURE;
+}