Add page 'ls_cache'

This new page will list all entries found in the current cache, which is
useful when reviewing the new cache implementation. There are no links to
the new page, but it's reachable by adding 'p=ls_cache' to any cgit url.

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

cache.h

@@ -26,6 +26,9 @@ extern int cache_process(int size, const char *path, const char *key, int ttl,
 			 cache_fill_fn fn, void *cbdata);
 
 
+/* List info about all cache entries on stdout */
+extern int cache_ls(const char *path);
+
 /* Print a message to stdout */
 extern void cache_log(const char *format, ...);