ui-shared: add cgit_print_layout_{start,end}()

These will avoid needing to call three functions to start page layout in
subsequent patches when we move the layout setup into each individual
page.

Signed-off-by: John Keeping <john@keeping.me.uk>

ui-shared.h

@@ -54,6 +54,9 @@ extern void cgit_object_link(struct object *obj);
 extern void cgit_submodule_link(const char *class, char *path,
 				const char *rev);
 
+extern void cgit_print_layout_start(void);
+extern void cgit_print_layout_end(void);
+
 __attribute__((format (printf,1,2)))
 extern void cgit_print_error(const char *fmt, ...);
 __attribute__((format (printf,1,0)))