mmime: ensure 7bit or 8bit Content-Transfer-Encoding for message/rfc822 parts

RFC 2046, Section 5.2.1:
> No encoding other than "7bit", "8bit", or "binary" is permitted for
> the body of a "message/rfc822" entity.

(We'll generate 8bit when we have to and put the blame on the MTA.)

mmime.c

@@ -219,11 +219,16 @@ gen_file(char *file, char *ct)
 			bithigh++;
 	}
 
-	if (strcmp(ct, "message/rfc822") == 0 && maxlinelen < 997)
-		maxlinelen = 0;
-
 	gen_attachment(filename, cd);
 
+	if (strcmp(ct, "message/rfc822") == 0) {
+		printf("Content-Type: %s\n", ct);
+		printf("Content-Transfer-Encoding: %dbit\n\n",
+		    (bitlow > 0 || bithigh > 0) ? 8 : 7);
+		fwrite(content, 1, size, stdout);
+		return 0;
+	}
+
 	if (bitlow == 0 && bithigh == 0 &&
 	    maxlinelen <= 78 && content[size-1] == '\n') {
 		if (!ct)