Add generic support for search box in page header

This adds the ability to show a search box in any pageheader with correct href and
hidden form data, but does not enable the box on any pages.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
diff --git a/ui-repolist.c b/ui-repolist.c
index 7090c12..9f12b18 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -17,7 +17,7 @@
 
 	chdir(cgit_root);
 	cgit_print_docstart(cgit_root_title, item);
-	cgit_print_pageheader(cgit_root_title);
+	cgit_print_pageheader(cgit_root_title, 0);
 
 	if (!(d = opendir("."))) {
 		cgit_print_error(fmt("Unable to scan repository directory: %s",