msgmerge: avoid printing too long line

this is one reason of #50.

One line is generally short, and [8192] is big enough for our usage. But
after cmake invokes msgmerge, lines are joined. So we printf some super
long lines into po files.

And again, cmake invokes msgfmt to use these updated po files. So we
meet these super long lines.

src/msgmerge.c

@@ -47,7 +47,7 @@ struct fiLes {
  * i.e. there is no translation lookup at all */
 int process_line_callback(po_message_t msg, void* user) {
 	struct fiLes* file = (struct fiLes*) user;
-	int i;
+	int i, j, k;
 	switch (file->stage) {
 	case ps_size:
 		if (msg->ctxt_len > file->len)
@@ -68,25 +68,40 @@ int process_line_callback(po_message_t msg, void* user) {
 	case ps_parse:
 		if (msg->ctxt_len) {
 			escape(msg->ctxt, file->buf, file->len);
-			fprintf(file->out, "msgctxt \"%s\"\n", file->buf);
+			fprintf(file->out, "msgctxt \"%.1024s\"\n", file->buf);
+			k = strlen(file->buf);
+			for (j = 1024; j < k; j += 1024)
+				fprintf(file->out, "\"%.1024s\"\n", &file->buf[j]);
 		}
 
 		escape(msg->id, file->buf, file->len);
-		fprintf(file->out, "msgid \"%s\"\n", file->buf);
+		fprintf(file->out, "msgid \"%.1024s\"\n", file->buf);
+		k = strlen(file->buf);
+		for (j = 1024; j < k; j += 1024)
+			fprintf(file->out, "\"%.1024s\"\n", &file->buf[j]);
 
 		if (msg->plural_len) {
 			escape(msg->plural, file->buf, file->len);
-			fprintf(file->out, "msgid_plural \"%s\"\n", file->buf);
+			fprintf(file->out, "msgid_plural \"%.1024s\"\n", file->buf);
+			k = strlen(file->buf);
+			for (j = 1024; j < k; j += 1024)
+				fprintf(file->out, "\"%.1024s\"\n", &file->buf[j]);
 		}
 
 		if (msg->plural_len) {
 			for (i=0; i < MAX_NPLURALS && msg->strlen[i]; i++) {
 				escape(msg->str[i], file->buf, file->len);
-				fprintf(file->out, "msgstr[%d] \"%s\"\n", i, file->buf);
+				fprintf(file->out, "msgstr[%d] \"%.1024s\"\n", i, file->buf);
+				k = strlen(file->buf);
+				for (j = 1024; j < k; j += 1024)
+					fprintf(file->out, "\"%.1024s\"\n", &file->buf[j]);
 			}
 		} else {
 			escape(msg->str[0], file->buf, file->len);
-			fprintf(file->out, "msgstr \"%s\"\n", file->buf);
+			fprintf(file->out, "msgstr \"%.1024s\"\n", file->buf);
+			k = strlen(file->buf);
+			for (j = 1024; j < k; j += 1024)
+				fprintf(file->out, "\"%.1024s\"\n", &file->buf[j]);
 		}
 
 		fputc('\n', file->out);