lib-storage: Add BROKENCHAR to mail_location

This makes the mailbox_list_settings.broken_char configurable. Mainly useful
with imapc when remote server doesn't contain valid mUTF-7 mailbox names.

src/lib-storage/mailbox-list.c

@@ -345,6 +345,13 @@ mailbox_list_settings_parse_full(struct mail_user *user, const char *data,
 		else if (strcmp(key, "FULLDIRNAME") == 0) {
 			set_r->index_control_use_maildir_name = TRUE;
 			dest = &set_r->maildir_name;
+		} else if (strcmp(key, "BROKENCHAR") == 0) {
+			if (strlen(value) != 1) {
+				*error_r = "BROKENCHAR value must be a single character";
+				return -1;
+			}
+			set_r->broken_char = value[0];
+			continue;
 		} else {
 			*error_r = t_strdup_printf("Unknown setting: %s", key);
 			return -1;