Scrap writerune(), introducing fputrune()

Interface and function as proposed by cls.
Code is also shorter, everything else analogous to fgetrune().

libutf/fputrune.c

@@ -0,0 +1,27 @@
+/* See LICENSE file for copyright and license details. */
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "../utf.h"
+
+int
+fputrune(const Rune *r, FILE *fp)
+{
+	char buf[UTFmax];
+
+	return fwrite(buf, runetochar(buf, r), 1, fp);
+}
+
+int
+efputrune(const Rune *r, FILE *fp, const char *file)
+{
+	int ret;
+
+	if ((ret = fputrune(r, fp)) < 0) {
+		fprintf(stderr, "fputrune %s: %s\n", file, strerror(errno));
+		exit(1);
+	}
+	return ret;
+}

libutf/writerune.c

@@ -1,23 +0,0 @@
-/* See LICENSE file for copyright and license details. */
-#include <errno.h>
-#include <stdio.h>
-#include <string.h>
-#include <stdlib.h>
-
-#include "../utf.h"
-
-void
-writerune(const char *file, FILE *fp, Rune *r)
-{
-	char buf[UTFmax];
-	int n;
-
-	if ((n = runetochar(buf, r)) > 0) {
-		fwrite(buf, n, 1, fp);
-		if (ferror(fp)) {
-			fprintf(stderr, "%s: write error: %s\n",
-				file, strerror(errno));
-			exit(1);
-		}
-	}
-}