cgit_open_filter: also take the repo as a parameter

To prepare for handing repo configuration to the
filter script that is executed.

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.h

@@ -318,7 +318,7 @@ extern const char *cgit_repobasename(const char *reponame);
 
 extern int cgit_parse_snapshots_mask(const char *str);
 
-extern int cgit_open_filter(struct cgit_filter *filter);
+extern int cgit_open_filter(struct cgit_filter *filter, struct cgit_repo * repo);
 extern int cgit_close_filter(struct cgit_filter *filter);
 
 extern int readfile(const char *path, char **buf, size_t *size);