about: always ensure page has a trailing slash

Otherwise we can't easily embed links to other /about/ pages.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
diff --git a/ui-shared.h b/ui-shared.h
index 1b8ecb5..43d0fa6 100644
--- a/ui-shared.h
+++ b/ui-shared.h
@@ -1,6 +1,8 @@
 #ifndef UI_SHARED_H
 #define UI_SHARED_H
 
+#include <stdbool.h>
+
 extern const char *cgit_httpscheme();
 extern const char *cgit_hosturl();
 extern const char *cgit_rooturl();
@@ -61,6 +63,7 @@
 extern void cgit_print_date(time_t secs, const char *format, int local_time);
 extern void cgit_print_age(time_t t, time_t max_relative, const char *format);
 extern void cgit_print_http_headers(void);
+extern void cgit_redirect(const char *url, bool permanent);
 extern void cgit_print_docstart(void);
 extern void cgit_print_docend();
 extern void cgit_print_pageheader(void);