Add ofs argument to cgit_log_link and use it in ui-log.c

This fixes a bug in the prev/next links on the log page: when on the default
branch the links to prev/next page would contain h=(null).

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-tree.c

@@ -93,7 +93,7 @@ static int ls_item(const unsigned char *sha1, const char *base, int baselen,
 
 	html("<td>");
 	cgit_log_link("log", NULL, "button", cgit_query_head, curr_rev,
-		      fullpath);
+		      fullpath, 0);
 	html("</td></tr>\n");
 	free(name);
 	return 0;