vlc_fixups.h: remove unused structure and enums

We only need to define them if they are used in an API but they are not. The
names are very generic and may collide with some defines, so avoid potential
compilation issues.

Only the VISIT enum is needed by twalk().

include/vlc_fixups.h

@@ -482,15 +482,6 @@ ssize_t sendmsg(int, const struct msghdr *, int);
 
 /* search.h */
 #ifndef HAVE_SEARCH_H
-typedef struct entry {
-    char *key;
-    void *data;
-} ENTRY;
-
-typedef enum {
-    FIND, ENTER
-} ACTION;
-
 typedef enum {
     preorder,
     postorder,